Expert: Abe Mantell - 1/12/2009

Question
Hi,


I have this question which I just can't figure out how they got the solution.

Q. The equation of the straight line that passes through the points (-2,5) and
(2,-5) is?

The answer is 7x-5y+45=0

I tried doing this via gradient form but they want it in intercept form, which I
don't know how to construct. Any help would be greatly appreciated. Thanks

Answer
Since we can express it as y=mx+b, we first need the slope...
slope, m=(5-(-5))/(-2-2)=10/(-4)=-5/2...so we have y=(-5/2)x+b
Now we can get 'b' by using one of the given points, (-2,5) say
==> 5=(-5/2)(-2)+b ==> 5=5+b ==> b=0...so the equation is simply
y=(-5/2)x (or y=-2.5x or 2y=-5x or 5x+2y=0).

Looks like the answer you have is waaaaay wrong!  Where did that
answer come from?

Abe