Desprate for some help! Quadratic Functions

Question

I don't normally ask for this extent of help. but can someone walk me through the last bit of this equation. I know the steps, but I keep getting it wrong, my teachers out of town, and I don't have anyone to help me.

Find the quadratic function y+ ax^2+ bx+ c whose graph passes through the given points.
(-2,-15) (-1,-4) (-3,-32)



So I have equations
1) -15=4x+2b+c

2) -4=a-b+c

3)-32=9a-3b+c

 

Then 1 and 2 give me : 3a+3b=-11  ------> (5) 15a+15b=-55

 

then 1 and 3 give me:5a-5b=-17 ----------> (3) 15a-15b=-51

 

but this doesn't seem right and i don't know where to go from here.

Answer 1

The first equation should be

 

-15 = 4a - 2b + c

 

 

The rest are okay.  Because of that error in the sign usage for the first equation, it screwed you over.  So just correct that on your part.