Question

perfect square v^2-16v+?

Answer 1

you take half of the v coefficient (-16) to get

-16/2 = -8

then you square this result to get (-8)^2 = 64

so the 64 replaces the question mark making

v^2 - 16v + 64

a perfect square

Answer 2

notice how v^2 - 16v + 64 factors to (v-8)^2, so that confirms the answer