19) (x + 2)² = 4
x + 2 = 2 hoặc x + 2 = -2
*) x + 2 = 2
x = 2 - 2
x = 0
*) x + 2 = -2
x = -2 - 2
x = -4
Vậy x = -4; x = 0
20) (2x - 3)² = 25
2x - 3 = 5 hoặc 2x - 3 = -5
*) 2x - 3 = 5
2x = 5 + 3
2x = 8
x = 8 : 2
x = 4
*) 2x - 3 = -5
2x = -5 + 3
2x = -2
x = -2 : 2
x = -1
Vậy x = -1; x = 4
21) (x + 4)² = 49
x + 4 = 7 hoặc x + 4 = -7
*) x + 4 = 7
x = 7 - 4
x = 3
*) x + 4 = -7
x = -7 - 4
x = -11
Váy x = -11; x = 3
22) (2x - 3)² = 36
2x - 3 = 6 hoặc 2x - 3 = -6
*) 2x - 3 = 6
2x = 6 + 3
2x = 9
x = 9/2
*) 2x - 3 = -6
2x = -6 + 3
2x = -3
x = -3/2
Vậy x = -3/2; x = 9/2
25)
(x + 2)³ = 64
(x + 2)³ = 4³
x + 2 = 4
x = 4 - 2
x = 2
26)
(2x - 1)³ = -8
(2x - 1)³ = (-2)³
2x - 1 = -2
2x = -2 + 1
2x = -1
27)
(3x + 1)³ = 27
(3x + 1)³ = 3³
3x + 1 = 3
3x = 3 - 1
3x = 2
