Đáp án:
12 - 2 . (-x + 3)² = -38
2 . (-x + 3)² = 12 - (-38)
2 . (-x + 3)² = 50
(-x + 3)² = 50 : 2
(-x + 3)² = 25
(-x + 3)² = 5²
(-x + 3)² = (-5)²
=> $\left \{ {{-x+3=5} \atop {-x+3=-5}} \right.$
=> $\left \{ {{-x=5-3} \atop {-x =-5-3}} \right.$
=> \(\left[ \begin{array}{l}-x=2\\-x=-8\end{array} \right.\)
=> $\left \{ {{x=-2} \atop {x=8}} \right.$
Vậy x = -2 hoặc x = 8.
-20 + 3 . (2x + 1) ³ = -101
3 . (2x + 1)³ = -101 - (-20)
3 . (2x + 1)³ = -81
(2x + 1)³ = -81 : 3
(2x + 1)³ = -27
(2x + 1)³ = (-3)³
=> 2x + 1 = -3
2x = -3 - 1
2x = -4
x = -4 : 2
x = -2
Vậy x = -2.
Chúc học tốt!!!
