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# GCSE Maths - How to answer this? watch

1. Hi, I have some homework due in tomorrow and I don't understand fully how to do it. Would appreciate help on how to answer this.

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2. Make one of the variables(x or y)the subject.
I'd make them the subject using the second equation given in each question!
3. Hi, yh its simple enough for me so I will explain. As you have got 2 equations you need to make the X or Y the same on both Equations. However, this seems to be better if you use substitution instead of Elimination <---- which you cant do for quadratics anyway, you can only use substitution. That is where you make one side equal either X or Y. For example the first question.
Rearrange the second equation to read x = y-1. Then substitute x = y-1 into y = (y-1)[squared] + 7(y-1) + 9, rearrange so the number is one one side and the y's on the other, that will tell you the value for Y. Ill do the first question after half an hour if you leave me to it hope this tho helped a little. After you know Y then sub it into the second equation to find x.
4. (Original post by TheMagicalWizard)
Hi, yh its simple enough for me so I will explain. As you have got 2 equations you need to make the X or Y the same on both Equations. However, this seems to be better if you use substitution instead of Elimination <---- which you cant do for quadratics anyway, you can only use substitution. That is where you make one side equal either X or Y. For example the first question.
Rearrange the second equation to read x = y-1. Then substitute x = y-1 into y = (y-1)[squared] + 7(y-1) + 9, rearrange so the number is one one side and the y's on the other, that will tell you the value for Y. Ill do the first question after half an hour if you leave me to it hope this tho helped a little. After you know Y then sub it into the second equation to find x.
Hi, would appreciate if you could give me the answer to the first one and walk me through step by step how you did it. I.E
Step 1) Factor in.... blah blah
Step 2) Make X = 0 or whatever

Thanks!
5. (Original post by iMacJack)
Hi, I have some homework due in tomorrow and I don't understand fully how to do it. Would appreciate help on how to answer this.

I think you would have to re-arrange the questions first and then solve the normally.
6. y=y

so x^2+7x+9=x+1

take away x and 1 from both sides

so x^2+6x+8=0

factorise

(x+4)(x+2)=0

x=-4 or x=-2

sub each of these into either of the first 2 equations

so when x=-4, y=-3

and when x=-2, y=-1

the two graphs meet at (-4, -3) and (-2, -1)
7. Hi guys, thanks.

For the second one, I attempted this:

I did X^2 + X + 9 = 2x + 6

So x^2 - x + 3 = 0

(x-1)(x+3) = 0
X = 1 or X = -3

Y = 2(1) + 6
Y = 8
1st pair = (1,8)

Y = 2(-3) + 6
Y = 0
2nd pair = (-3,0)

Where did I go wrong? Thanks!
8. I think you miscopied the LHS and then you factorised incorrectly.
9. (Original post by iMacJack)
Hi guys, thanks.

For the second one, I attempted this:

I did X^2 + X + 9 = 2x + 6

So x^2 - x + 3 = 0

(x-1)(x+3) = 0
X = 1 or X = -3

Y = 2(1) + 6
Y = 8
1st pair = (1,8)

Y = 2(-3) + 6
Y = 0
2nd pair = (-3,0)

Where did I go wrong? Thanks!
It should be .

As a side note, the quadratic you found didn't factorise, so you would have to complete the square or use the quadratic formula in future.
10. (Original post by morgan8002)
It should be .

As a side note, the quadratic you found didn't factorise, so you would have to complete the square or use the quadratic formula in future.
Yep. You're right hahhaahahaha. I read my own writing wrong when I was working it out. Uh-oh. Thanks!
11. Hi all, I restarted it and got 100% on the first question, thanks to you guys helping me I fully understand that!

Now, on the second page of Q's, I came across this, can anyone advice me on how to tackle these?

Thank you!!!!

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12. (Original post by iMacJack)
Hi all, I restarted it and got 100% on the first question, thanks to you guys helping me I fully understand that!

Now, on the second page of Q's, I came across this, can anyone advice me on how to tackle these?

Thank you!!!!

For each, substitute the linear equation into the quadratic one.
13. Yes, so in the first example replace y by (x - 2).

You will then have a quadratic in x to solve.

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Updated: January 22, 2015
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