http://www.emaths.co.uk/sats/2009/2009_68_Paper1.pdf

please go to question 24 and help me answer(Wait)(Crying)

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- Feb 13th 2010, 04:29 AMcoolubicoordinates
http://www.emaths.co.uk/sats/2009/2009_68_Paper1.pdf

please go to question 24 and help me answer(Wait)(Crying) - Feb 13th 2010, 04:41 AMmathemagister
This looks a lot like a test, so here is just a hint:

Notice they have told you the two equations you need to deal with. You have 2 variables and 2 equations. Do you know how to solve simultaneous equations? When you solve for x and y, make sure you pair up the right numbers with each other for the 2 points.

Feel free to ask if you need any more help. - Feb 13th 2010, 04:52 AMcoolubi
- Feb 13th 2010, 05:44 AMmathemagister
The information tells you that at the points A and B, [b]both[/both] the equations and are correct for the same x and y values.

So, to solve for the intercepts, you need to simultaneously solve the equations

and .

You know that , so anywhere you see a , you are allowed to substitute it for because they are both the same thing. (Think of it like if you know , you can put wherever you see a .

Well, you see a in the second equation; you can substitute that for something else that equals it: .

This gives you:

and

to find the y value for these points simply plug them into one of the original equations:

These give you the points (0,-2) and (1,-1).

Since you can see on the graph that point A lies on the y-axis (where x is always 0), you know that point A is (0,-2) and point B has to therefore be (1,-1).

Hope that helps :)