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Blush Babe
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Help!! The exam is in a few days and I’m confused… :confused:
This is for the maths as-level exam:
1) The line with equation y = 3x + 1 cut the curve with equation y = x^2 + 4x – 5 at the points A and B. Find the length of AB.
(I found the coordinates A(-3, -8) and B(2, 6) but I don’t know what to do next…)

2) On a journey, the average speed of a car is v m s^-1. For v to be bigger or equal to 5, the cost per kilometre, C pence, of the journey is modelled by: C = 160/v + v^2/100
Using this model,
a) Show, by calculus, that there is a value of v for which C has a stationary value, and find this value of v.
b) Justify that this value of v gives a minimum value of C.
c) Find the minimum value of C and hence find the minimum cost of a 250 km car journey.
(I didn’t even know we DID calculus, whatever it is, is this in the syllabus cuz it’s not in my Edexcel book)

3) Straight line L1 crosses the y-axis with the equation y = 3/2x – 2. The point Q has the coordinates (5, -3). Straight line L2 is perpendicular to L1 and passes through Q.
a) Find the equation for L2 in the form ax + by = c, where a, b and c are integer constants.
Would appreciate any help given .
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gzftan
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(Original post by Blush Babe)
Help!! The exam is in a few days and I’m confused… :confused:
This is for the maths as-level exam:
1) The line with equation y = 3x + 1 cut the curve with equation y = x^2 + 4x – 5 at the points A and B. Find the length of AB.
(I found the coordinates A(-3, -8) and B(2, 6) but I don’t know what to do next…)

2) On a journey, the average speed of a car is v m s^-1. For v to be bigger or equal to 5, the cost per kilometre, C pence, of the journey is modelled by: C = 160/v + v^2/100
Using this model,
a) Show, by calculus, that there is a value of v for which C has a stationary value, and find this value of v.
b) Justify that this value of v gives a minimum value of C.
c) Find the minimum value of C and hence find the minimum cost of a 250 km car journey.
(I didn’t even know we DID calculus, whatever it is, is this in the syllabus cuz it’s not in my Edexcel book)

3) Straight line L1 crosses the y-axis with the equation y = 3/2x – 2. The point Q has the coordinates (5, -3). Straight line L2 is perpendicular to L1 and passes through Q.
a) Find the equation for L2 in the form ax + by = c, where a, b and c are integer constants.
Would appreciate any help given .
BB
For question one...you have the co-ordinates....use these to find horizontal and vert distance then use pythagoras' theorum.

Wait for question 2....i haven't read it yet...

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gzftan
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Erm...not too sure on question 2....cos i don't fully understand the question!

But....i think that it wants you to treat C=...etc. as the formula for a curve...so differentiate it and set to 0 (i.e. stationary points), then finish the question.

Question3...find perpendicular gradient for L1...sub it ito the formula for a straight line using Q as reference points...and rearrange to find L2's equation...hope it helps.

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Blush Babe
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(Original post by gzftan)
For question one...you have the co-ordinates....use these to find horizontal and vert distance then use pythagoras' theorum.

Wait for question 2....i haven't read it yet...

G
Thanks for Qs 1....Im so thick
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Nylex
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Calculus is differentiation and integration. Surely "stationary value" makes you think of differentiating?
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gzftan
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(Original post by Blush Babe)
Thanks for Qs 1....Im so thick
No probs....sometimes i miss the simplest things...and then someone points it out to me...and i feel like a right plonker!

Seriously tho...sometimes your mind gets stuck in one way of doing something...so when the time comes to use a different method...you can't see it! Just take your time when answering questions...and try and look at it from as many different angles (haha..maths pun!!) as possible.

I find that helps loads, hope it helps you.

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Linx
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Help!! i have a psychology exam in a few days and i have sooo many names and dates to remember i don't know where to start, any tips would probably save my life!! thanks.
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Blush Babe
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(Original post by Nylex)
Calculus is differentiation and integration. Surely "stationary value" makes you think of differentiating?
Oh....so you use diff to find the gradient/acceleration...Sorry if I'm stating the obvious but our teacher sucks and he never told us what they're used for. Thanks though.
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Blush Babe
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#9
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(Original post by gzftan)
No probs....sometimes i miss the simplest things...and then someone points it out to me...and i feel like a right plonker!

Seriously tho...sometimes your mind gets stuck in one way of doing something...so when the time comes to use a different method...you can't see it! Just take your time when answering questions...and try and look at it from as many different angles (haha..maths pun!!) as possible.

I find that helps loads, hope it helps you.

G
LOL. Cheers.
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Blush Babe
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#10
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(Original post by Linx)
Help!! i have a psychology exam in a few days and i have sooo many names and dates to remember i don't know where to start, any tips would probably save my life!! thanks.
Names and dates? Sounds like history....just keep writing them down, even rhyme them if it helps . You can also record them on a tape and play it to yourself whilst you are sleeping. Also post-it them on your bathroom mirror so you see them, and hopefully memorise them, while you're brushing teeth and doing other essential groomings .
Hope this helps...
BB
P.S. I never tried any of them cuz I'm too lazy but the things I come up with....I should write a book.
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