Question

Which one of the following values of k makes the trinomial 9x^2 + kx + 64 a perfect square

a 24
b 48
c 16
d 42

Answer 1

it is C 16

Explanation:

x² - kx + 64

Since we are looking for a perfect square, then we need to take the square root of 64 to find the factors: √64 = 8

So, the factors are: (x - 8)(x - 8)

Foil (or distribute) to get: x² - 16x + 64 The k-value is 16