Solve x2 + 20x + 100 = 36 for x.
a. x = –16 or x = –4
b. x = –10
c. x = –8
d. x = 4 or x = 16

X² + 20x + 100 = 36⇒ x² + 20x + 100 - 36 = 0⇒ x² + 20x + 64 =0

Δ = b²-4ac = 20² -4·1·64 = 400-256 = 144

x₁= (-b+√Δ)/2a = (-20+√144)/2·1 = (-20+12)/2 = -8/2 = -4
x₂= (-b-√Δ)/2a = (-20-√144)/2·1 = (-20-12)/2 = -32/2 = -16

x=-4 or x=-16

How much is 32 out of 40 written as a percentage? convert fraction (ratio) 32 / 40 answer:   80%