Question

What is the y-value of the vertex of the function f(x) = –(x – 3)(x + 11)?

Answer 1

You can factor it out to get -x^2-8x+33, since the x of vertex is -b/2a, the x coordinate is -4, and plug it back in you would get 49

Answer 2

Answer:

49.

Step-by-step explanation:

We have been a function $f(x)=-(x-3)(x+11)$. We are asked to find the y-value of vertex of the given function.  

Upon multiplying both factors, we will get,

$f(x)=-(x*x+11*x-3*x-3*11)$

$f(x)=-(x^2+11x-3x-33)$

$f(x)=-(x^2+8x-33)$

$f(x)=-x^2-8x+33$        

Now, we  will use $\frac{-b}{2a}$ formula to find the x-coordinate of vertex of parabola.

$\frac{--8}{2*-1}$

$\frac{8}{-2}$

$-4$

Since the x-coordinate of vertex of parabola is $-4$, so we will substitute $x=-4$ in our equation to find y-coordinate of parabola.

$f(-4)=-(-4)^2-8(-4)+33$  

$f(-4)=-16+32+33$  

$f(-4)=49$  

Therefore, the y-coordinate of vertex of the given parabola is 49.