[Math] Find equation of a parabola given slope of tangent line at two x values and a point on the curve

calculusderivativestangent line

I'm stuck on this Calculus problem about finding a parabola with the equation

$y=ax^2+bx+c$

I know the slope of $3$ at x=1 and slope of $-13$ at $x=-1$, and know that the parabola passes through the point $(1,1).$

Any help would be great.

Best Answer

Let $f(x)=ax^{2}+bx+c$. We know the following:

\begin{cases} f'(1)=2a+b=3\\ f'(-1)=-2a+b=-13\\ f(1)=a+b+c=1 \end{cases}

This system has solution $a=4, b=-5$ and $c=2$. So the parabola you are looking for has equation $$y=4x^{2}-5x+2.$$