Question

Identify the vertex for the graph of y = −2x2 + 8x − 1.

(−2, 7)<---- my answer

(2, 7)

(2, −9)

(−2, −9)

Answer 1

I got a different answer. Try taking the derivative, and set it to 0. Then plug in that x value into the original equation.

Answer 2

what s the derivative?

Answer 3

Wait, how did you calculate your answer?

Answer 4

I did this from a calculus perspective, but you might have another way of doing it.

Answer 5

i did it kind of like simplifying but idk if its right. i did -2 cu i think thats the x value and 8-1 which is positive 7 ? i dont really know how to do this stuff.

Answer 6

Okay, to take the derivative, you go nx^n-1. n is the exponent on the x. The derivative of any constant is zero. So the derivative of your equation is -4x + 8. Set that to zero, and plug in the x value into your original equation.