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# OCR (not MEI) C1 - Wednesday 13th May 2015 watch

1. (Original post by marioman)
This isn't correct. You only change the sign when dividing by a negative number (an integer or otherwise).
Oops, my bad. Trying to do too many things at once haha Was thinking of logs as this is where they usually come up where for example, ln0.7 is negative. Fixed it now, thanks for pointing it out.
2. (Original post by kawehi)
Does anyone have any particularly difficult questions that they've come across?
This applications of differentiation question was an interesting one too (from June 2006)
3. Awkies thanks you're both beautiful xxxxx

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4. (Original post by Saraaliakaqueen)
Ohmygoodness why didnt i join this website before. You have been so helpful! May u get all the A*s in the world you absolute BABE

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You're welcome! Just note what somebody said below about a mistake I made - flip the sign when you divide by a negative, not a decimal. Had a stupid moment!
5. (Original post by Saraaliakaqueen)
Awkies thanks you're both beautiful xxxxx

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Oh another thing, if you have x^2 > 16, don't say x^2 > +/- 4. Change this to x^2 - 16 > 0 then solve as I showed with the quadratics before
6. A couple of (hopefully useful) things for everyone taking the exam tomorrow:

- Parallel lines have the same gradients, as do tangents to curves and circles (at that specific point only). Gradients of straight lines are found from (y2-y1)/(x2-x1) whereas you use differentiation if it's a curve.

- Perpendicular/normal lines will obey the rule m1 x m2 = -1. The easy way to think of this is "flip and change sign" e.g. if gradient = 3, gradient of normal = -1/3.

- Quadratics with a positive x^2 term show a "smiley face" shaped parabola, negative x^2 terms show a "sad face".

- At stationary/turning points, the gradient is 0.

- If a question asks for a sketch of a graph, show all points on intersection with the axes and, if relevant, turning points. Remember, graphs cross the y axis when x=0 and the x axis when y=0.

- If you're using any sort of formula, it's a good idea to write the formula before you substitute in numbers. If you mess the substitution up, you will still get marks for the correct formula whereas if you don't give the formula, you won't.

- An easy way to find turning points is by completing the square - if you end up with a(x+b)^2 + c, the TP will be at (-b, c). Lines of symmetry go through turning points.

- Quadratics in disguise must have two powers on the variables, one of which is double the other. Substitute in y (or whatever you want to call it) for the smaller power and y^2 for the larger power. You must remember to change y back to x (or equivalent, depends on what they give you) when you are finished.

- If you are differentiating a function which consists of two brackets, for example, expand the brackets and then differentiate. You can't differentiate two brackets which multiply each other without using the product rule, and you have to wait until C3 for the excitement of that.

- When curves intersect, put the two equations equal to each other and solve simultaneously.

- Difference of two squares: x^2 - 25 = (x+5)(x-5). Similarly, x^2 - any square number will factorise to (x + root of number)(x - root of number).

- Positive square numbers have two roots: the positive and negative root (not sure how to word that). e.g. the square roots of 16 are +4 and -4.

- When applying differentiation, always check your answers with the situation they give you and adjust accordingly. By this I mean things like you can't have a negative area, check whether it states that only integers are possible.

- Always simplify your answers as much as possible. 57/27 = 19/9.

- A quick way to see if an answer is divisible by 3 (or 6, 9 etc) is to see if the digits add up to a number that is divisible by 3. For example, try 2190. 2+1+9+0 = 12, which is divisible by 3 therefore 2190 is also divisible by 3. This won't show you what 2190/3 is (it's 730 btw) but it'll save you time from trying to divide into a number that doesn't divide.

- Never leave anything blank, it's a guaranteed 0. Even writing something gives you the possibility of some marks.

- Check your work at the end (if you have time of course) - don't sit around doing nothing. Silly mistakes are easy and stupid ways to throw away marks and can be easily fixed.

- Exact values mean leave your answer as a surd, in terms of pi etc.

- Probably won't apply much on a non-calculator paper, but the general rule is to give answers to 3sf.

- Remember this is a non-calculator paper, so if halfway through an answer you realise you're ending up with really weird numbers which are going to almost impossible to use later on, look back to see if there's anywhere you could have made an error. Sometimes final answers are 'weird' but the exam isn't designed to test your knowledge of multiplying 36474 by 1745 in the middle of a differentiation question.

- If you have two answers, pick one. I think they have to assume the incorrect one(s) is/are your given answer if you leave multiple answers.

Good luck!
7. I'm feeling a little more confident with the applications of differentiation now...just worried that if I **** up on a question tomorrow I could end up dropping a grade boundary or two thanks to how high they are.
8. (Original post by scrlk)
I'm feeling a little more confident with the applications of differentiation now...just worried that if I **** up on a question tomorrow I could end up dropping a grade boundary or two thanks to how high they are.
Are you looking forward to C2 ?

I'm going to madly revise tomorrow at school for C2 with a friend after C1.
9. (Original post by Peppercrunch)
Are you looking forward to C2 ?

I'm going to madly revise tomorrow at school for C2 with a friend after C1.
Of course.

C2 is much more interesting than C1.

Saying that I messed it up really badly last year, my exam season was a total disaster with further maths (M2...never again!) and I ended up repeating the AS year which has been pretty dire.
10. Does anybody know of a thread for C1 for edexcel? Thanks

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11. (Original post by Clovers)
Does anybody know of a thread for C1 for edexcel? Thanks

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http://www.thestudentroom.co.uk/show...ght=c1+edexcel
12. Just a quick question, when doing the quadratic formula, do you simplify everything on top before dividing through by the denominator (that is if the denominator is a factor)

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13. (Original post by jampot98)
Just a quick question, when doing the quadratic formula, do you simplify everything on top before dividing through by the denominator (that is if the denominator is a factor)

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Yeah, easiest to simplify the surd expression then, if possible, cancel with the denominator
14. (Original post by chloe-jessica)
Yeah, easiest to simplify the surd expression then, if possible, cancel with the denominator
Thanks. And good luck tomorrow

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15. (Original post by jampot98)
Thanks. And good luck tomorrow

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You too!
16. (Original post by chloe-jessica)
A couple of (hopefully useful) things for everyone taking the exam tomorrow:

- Parallel lines have the same gradients, as do tangents to curves and circles (at that specific point only). Gradients of straight lines are found from (y2-y1)/(x2-x1) whereas you use differentiation if it's a curve.

- Perpendicular/normal lines will obey the rule m1 x m2 = -1. The easy way to think of this is "flip and change sign" e.g. if gradient = 3, gradient of normal = -1/3.

- Quadratics with a positive x^2 term show a "smiley face" shaped parabola, negative x^2 terms show a "sad face".

- At stationary/turning points, the gradient is 0.

- If a question asks for a sketch of a graph, show all points on intersection with the axes and, if relevant, turning points. Remember, graphs cross the y axis when x=0 and the x axis when y=0.

- If you're using any sort of formula, it's a good idea to write the formula before you substitute in numbers. If you mess the substitution up, you will still get marks for the correct formula whereas if you don't give the formula, you won't.

- An easy way to find turning points is by completing the square - if you end up with a(x+b)^2 + c, the TP will be at (-b, c). Lines of symmetry go through turning points.

- Quadratics in disguise must have two powers on the variables, one of which is double the other. Substitute in y (or whatever you want to call it) for the smaller power and y^2 for the larger power. You must remember to change y back to x (or equivalent, depends on what they give you) when you are finished.

- If you are differentiating a function which consists of two brackets, for example, expand the brackets and then differentiate. You can't differentiate two brackets which multiply each other without using the product rule, and you have to wait until C3 for the excitement of that.

- When curves intersect, put the two equations equal to each other and solve simultaneously.

- Difference of two squares: x^2 - 25 = (x+5)(x-5). Similarly, x^2 - any square number will factorise to (x + root of number)(x - root of number).

- Positive square numbers have two roots: the positive and negative root (not sure how to word that). e.g. the square roots of 16 are +4 and -4.

- When applying differentiation, always check your answers with the situation they give you and adjust accordingly. By this I mean things like you can't have a negative area, check whether it states that only integers are possible.

- Always simplify your answers as much as possible. 57/27 = 19/9.

- A quick way to see if an answer is divisible by 3 (or 6, 9 etc) is to see if the digits add up to a number that is divisible by 3. For example, try 2190. 2+1+9+0 = 12, which is divisible by 3 therefore 2190 is also divisible by 3. This won't show you what 2190/3 is (it's 730 btw) but it'll save you time from trying to divide into a number that doesn't divide.

- Never leave anything blank, it's a guaranteed 0. Even writing something gives you the possibility of some marks.

- Check your work at the end (if you have time of course) - don't sit around doing nothing. Silly mistakes are easy and stupid ways to throw away marks and can be easily fixed.

- Exact values mean leave your answer as a surd, in terms of pi etc.

- Probably won't apply much on a non-calculator paper, but the general rule is to give answers to 3sf.

- Remember this is a non-calculator paper, so if halfway through an answer you realise you're ending up with really weird numbers which are going to almost impossible to use later on, look back to see if there's anywhere you could have made an error. Sometimes final answers are 'weird' but the exam isn't designed to test your knowledge of multiplying 36474 by 1745 in the middle of a differentiation question.

- If you have two answers, pick one. I think they have to assume the incorrect one(s) is/are your given answer if you leave multiple answers.

Good luck!
How would I do question 10(iii) ?
https://8d805163f22accfa62d3038a6f88...20C1%20OCR.pdf
How would I do question 10(iii) ?
https://8d805163f22accfa62d3038a6f88...20C1%20OCR.pdf
Differentiate and make dy/dx = 4 as this is the gradient of the straight line find x and y values of this point them sub in this point to find c.
18. (Original post by jonnydowe)
Differentiate and make dy/dx = 4 as this is the gradient of the straight line find x and y values of this point them sub in this point to find c.
Thank you so much !
How would I do question 10(iii) ?
https://8d805163f22accfa62d3038a6f88...20C1%20OCR.pdf
What was said above is right.
Gradient of straight line is 4 (y=mx+c) and you can differentiate the curve to get dy/dx = 6x - 14. You know this has to equal 4 (tangents have same gradient) therefore 6x - 14 = 4, 6x = 18, x = 3. Find the y coordinate at x = 3 by putting back into the equation of the curve: y = 3(3)^2 - 14(3) - 5 = 27 - 42 - 5 = -20.
Use these x and y values in the y=4x+c equation to get -20=4(3)+c, c = -32.
Alternatively use y - y1 = m(x - x1)
y + 20 = 4(x - 3)
y = 4x - 12 - 20
y = 4x - 32, therefore c = -32.
20. (Original post by chloe-jessica)
A couple of (hopefully useful) things for everyone taking the exam tomorrow:

- Parallel lines have the same gradients, as do tangents to curves and circles (at that specific point only). Gradients of straight lines are found from (y2-y1)/(x2-x1) whereas you use differentiation if it's a curve.

- Perpendicular/normal lines will obey the rule m1 x m2 = -1. The easy way to think of this is "flip and change sign" e.g. if gradient = 3, gradient of normal = -1/3.

- Quadratics with a positive x^2 term show a "smiley face" shaped parabola, negative x^2 terms show a "sad face".

- At stationary/turning points, the gradient is 0.

- If a question asks for a sketch of a graph, show all points on intersection with the axes and, if relevant, turning points. Remember, graphs cross the y axis when x=0 and the x axis when y=0.

- If you're using any sort of formula, it's a good idea to write the formula before you substitute in numbers. If you mess the substitution up, you will still get marks for the correct formula whereas if you don't give the formula, you won't.

- An easy way to find turning points is by completing the square - if you end up with a(x+b)^2 + c, the TP will be at (-b, c). Lines of symmetry go through turning points.

- Quadratics in disguise must have two powers on the variables, one of which is double the other. Substitute in y (or whatever you want to call it) for the smaller power and y^2 for the larger power. You must remember to change y back to x (or equivalent, depends on what they give you) when you are finished.

- If you are differentiating a function which consists of two brackets, for example, expand the brackets and then differentiate. You can't differentiate two brackets which multiply each other without using the product rule, and you have to wait until C3 for the excitement of that.

- When curves intersect, put the two equations equal to each other and solve simultaneously.

- Difference of two squares: x^2 - 25 = (x+5)(x-5). Similarly, x^2 - any square number will factorise to (x + root of number)(x - root of number).

- Positive square numbers have two roots: the positive and negative root (not sure how to word that). e.g. the square roots of 16 are +4 and -4.

- When applying differentiation, always check your answers with the situation they give you and adjust accordingly. By this I mean things like you can't have a negative area, check whether it states that only integers are possible.

- Always simplify your answers as much as possible. 57/27 = 19/9.

- A quick way to see if an answer is divisible by 3 (or 6, 9 etc) is to see if the digits add up to a number that is divisible by 3. For example, try 2190. 2+1+9+0 = 12, which is divisible by 3 therefore 2190 is also divisible by 3. This won't show you what 2190/3 is (it's 730 btw) but it'll save you time from trying to divide into a number that doesn't divide.

- Never leave anything blank, it's a guaranteed 0. Even writing something gives you the possibility of some marks.

- Check your work at the end (if you have time of course) - don't sit around doing nothing. Silly mistakes are easy and stupid ways to throw away marks and can be easily fixed.

- Exact values mean leave your answer as a surd, in terms of pi etc.

- Probably won't apply much on a non-calculator paper, but the general rule is to give answers to 3sf.

- Remember this is a non-calculator paper, so if halfway through an answer you realise you're ending up with really weird numbers which are going to almost impossible to use later on, look back to see if there's anywhere you could have made an error. Sometimes final answers are 'weird' but the exam isn't designed to test your knowledge of multiplying 36474 by 1745 in the middle of a differentiation question.

- If you have two answers, pick one. I think they have to assume the incorrect one(s) is/are your given answer if you leave multiple answers.

Good luck!
Im still abit muddled on stationary points,increasing and decreasing fucntions and when to use the second deritive ?

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