@Holliwood#: @ TEAM_IQ_2000#:
Đáp án:
x = 3
Giải thích các bước giải:
∛x-2 + √x+1 = 3
⇔ ∛x-2 = 3 - √x+1
⇔ x-2=27-27√x+1 +3.3(x+1)-√(x+1)³
⇔ x-2=27-27√x+1+9x+9+(-x-1)√x+1
⇔ x-2=36-27√x+1 +9x+(-x-1)√x+1
⇔ x-2-36-9x=-27√x+1 +(-x-1)√x+1
⇔ -8x-38=-√x+1 . (28+x)
⇔ 8x+38=√x+1 . (28+x)
⇔ 64x²+608x+1444=(x+1).(28+x)²
⇔ 64x²+608x+1444=(x+1).(784+56x+x²)
⇔ 64x²+608x+1444=784x+56x²+x³+784+56x+x²
⇔ 64x²+608x+1444=840x+57x²+x³+784
⇔ 64x²+608x+1444-840x-57x²-x³-784=0
⇔ 7x²-232x+660-x³=0
⇔ -x³+7x²-232x+660=0
⇔ -x³+3x²+4x²-12x-220x+660=0
⇔ -x².(x-3)+4x.(x-3)-220(x-3)=0
⇔ -(x-3).(x²-4x+220)=0
⇔ (x-3).(x²-4x+220)=0
⇔$\left \{ {{x-3=0} \atop {x²-4x+220=0}} \right.$
⇔ $\left \{ {{x=3} \atop {x∉ R}} \right.$
⇒ x = 3
⇔ ∛3-2 + √3+1 = 3
⇔ 3 = 3
⇒ x = 3
Vậy x = 3
Bn tham khảo nhé!!!!!!!!!!!!!!!!!!!!!!!!!
Xin ctlhn ạ!!!!!!!!!!!!!!!!!!!!
