[Charries]

AQA GCSE NOn Calculator paper often has a quadratic equation and a graph. They then give you another quadratic or a linear equation and ask you to find another that provides solutions, which involved the subrtaction of one of the given equations from the other. What is the rule for which equation is taken from which other, as sometimes I get this the right way round and sometimes i don't. i.e. sometimes i get the answer on the mark scheme (e.g. y=mx+c) and sometimes i get the negative (y=-mx-c) since i have taken them the wrong way round.

[boromir9111]

make them equal to another cause if it's "y =..." for both of them then you can make them equal and bring it on to one side by subtracting to make it equal to 0... you bring it into the one that has the quadratic and that's usually on the left side.

[steve2005]

Originally Posted by Charries

AQA GCSE NOn Calculator paper often has a quadratic equation and a graph. They then give you another quadratic or a linear equation and ask you to find another that provides solutions, which involved the subrtaction of one of the given equations from the other. What is the rule for which equation is taken from which other, as sometimes I get this the right way round and sometimes i don't. i.e. sometimes i get the answer on the mark scheme (e.g. y=mx+c) and sometimes i get the negative (y=-mx-c) since i have taken them the wrong way round.

Can you post one of the questions that you got wrong.

[steve2005]

Originally Posted by Charries

AQA GCSE NOn Calculator paper often has a quadratic equation and a graph. They then give you another quadratic or a linear equation and ask you to find another that provides solutions, which involved the subrtaction of one of the given equations from the other. What is the rule for which equation is taken from which other, as sometimes I get this the right way round and sometimes i don't. i.e. sometimes i get the answer on the mark scheme (e.g. y=mx+c) and sometimes i get the negative (y=-mx-c) since i have taken them the wrong way round.

Here is an example

[Charries]

yes - moduel 3, Nove 2006 :

we were asked to plot - graph of y = x^2 +3x -2
then asked to find solutions to x^2 +3x - 2 = 0

all ok so far.

Now asks, by drawing a linear graph on the same axis, find solutions of the equation x^2 -3 = 0

- i picked up some marks on my answer of y=-3x -1, but it appears it should be y=-3x-1 - i obviously took them the wrong way round.

[Charries]

Oik =- what i do is line one below the other an take them, so I will try to understand what you are saying and why i cannot do this

[Charries]

I think I have it - i was just taking the right hand side of the eqn and forgetting about the y. I can line them up and take, but in my example i would have had a negative y, in which case i would have got the right answer. Thanks a lot.

[steve2005]

Originally Posted by Charries

yes - moduel 3, Nove 2006 :

we were asked to plot - graph of y = x^2 +3x -2
then asked to find solutions to x^2 +3x - 2 = 0

all ok so far.

Now asks, by drawing a linear graph on the same axis, find solutions of the equation x^2 -3 = 0

- i picked up some marks on my answer of y=-3x -1, but it appears it should be y=-3x-1 - i obviously took them the wrong way round.