# Writing an Equation.

• Jul 30th 2008, 11:16 AM
JoeF107
Writing an Equation.
Question:

Write a Determine the values of b and c such that f(x) = x^2 + bx + c passes through the points (-4,0) and (3,14)

I'm not sure how to approach the problem. I have tried using vertex version of quadratic formula a(x-h)^2+k, but the problem does not specify which ordered pair is the vertex. I also tried plugging into the ordered pairs into my graphing calc, and got an error because I need three ordered pairs for it to give me an expression.

Suggestions?
• Jul 30th 2008, 12:05 PM
flyingsquirrel
Hi
Quote:

Originally Posted by JoeF107
Question:

Write a Determine the values of b and c such that f(x) = x^2 + bx + c passes through the points (-4,0) and (3,14) [...]

Suggestions?

We know that the curve passes through $(-4,0)$ and $(3,14)$ which means that $f(-4)=0$ and that $f(3)=14$. Using these two equalities, can you find the value of $b$ and $c$ ?
• Jul 30th 2008, 01:01 PM
JoeF107
Quote:

Originally Posted by flyingsquirrel
Hi

We know that the curve passes through $(-4,0)$ and $(3,14)$ which means that $f(-4)=0$ and that $f(3)=14$. Using these two equalities, can you find the value of $b$ and $c$ ?

ah, I was over thinking the problem. thanks :)
• Jul 31st 2008, 07:38 AM
tutor
16-4b+c=3
9+3b+c=14

subtracting above equations

-7b=-18
b=18/7

substitute b=18/7 in -4b+c=-13
then c=-19/7