Penjelasan dengan langkah-langkah:

1). 4x² - 4x - 15 = 0

a = 4 , b = -4 dan c = -15

.

d = b/2a = -4/2(4)= -4/8= -1/2

e = c - (b²/4a)= -15- ((-4)²/4(4)= (-15 - 16/16)= (-15-1)= -16

a(x + d)² = -e

4(x - 1/2)² = -(-16)

4(x - 1/2)² = 16

(x - 1/2)² = 16/4

(x - 1/2)² = 4

(x - 1/2) = ±√4

(x - 1/2)= ±2

x1 = 2+1/2= 5/2 atau x2 = -2+1/2= -3/2

.

2). 6x² + 17x + 12 = 0

a = 6. b = 17 , c = 12

d = b/2a = 17/2(6)= 17/12

e = c - (b²/4a) = 12 - (17²/4(6)= (12 - 289/24)= (288-289)/24 = -1/24

.

a(x + d)² = -e

6(x + 17/12)² = 1/24

(x + 17/12)² = 1/24 : 6/1

(x + 17/12)² = 1/24 . 1/6

(x + 17/12)² = 1/144

(x + 17/12)= ±√(1/144)

(x + 17/12)= ±1/12

x1 = 1/12 - 17/12 = -16/12 = -4/3

atau

x2 = -1/12 - 17/12 = -18/12 = -3/2