What are the solutions to the quadratic equation 3(x − 4)2 = 75?

a. x = −9 and x = 1
b. x = −5 and x = 5
c. x = −4 and x = 4
d. x = −1 and x = 9

3(x - 4)² = 75
(x - 4)² = 25

(a - b)² = a² - 2ab + b²

x² - 2*1x*4 + 4² = 25
x² - 8x + 16 = 25
x² - 8x + 16 - 25 = 25 - 25
x² - 8x -9 = 0

a=1   b = -8   c= -9

Δ = b² - 4ac = (-8)² - 4 *1*(-9) = 64 +36 = 100
√Δ = 10

 



Answer D

The density of the cube is 40