(12 - 2) * 180 = 1,800/12 = 150
(8 - 2) * 180 = 1,080/8 = 135
B. 8 sides
Put the value of x = -1 to the equation of a function f(x):

Step-by-step explanation:
To complete the square, take half of the second coefficient, square it, then add the result to both sides.
(-8/2)² = (-4)² = 16
x² − 8x + 16 = 9 + 16
Solving:
(x − 4)² = 25
x − 4 = ±5
x = 4 ± 5
x = -1 or 9