Question

Identify the vertex for the graph of y = 2x2 + 8x − 3.

(2, 21)

(2, 17)

(−2, −11)

(−2, −27)

Answer 1

-b/2a defines the x value of the vertex

Answer 2

or if you use calculus techniques, f' = 0 also works

Answer 3

i dont know what either of them means

Answer 4

then how have you been finding the vertex before?

Answer 5

i dont quite remember. see i went on vacation for 2 weeks and i dont really remember much

Answer 6

well, we can narrow it down, since the same x value cant possibly have different y values.

solve for x=2 and x=-2 to eliminate some options

Answer 7

since the first term is positive, and this is an even degreed equation, i now itll resemble "U" in shape. the vertex is the lowest value in this case.

once you narrow down the options, look for the one with the smallest y value

Answer 8

i think its the third option but im not sure

Answer 9

when x=-2, does the value of the equation equal -11?

Answer 10

yes

Answer 11

then since that is true, and its y value is the smallest of the options; its got to be correct

Answer 12

thanks for youre help @amistre

Answer 13

good luck ;)