Question

2. Tìm x: ( x - 2 ) ³ - ( x + 1 ) ³ + 9x ( x + 1 ) - 9 = 0

Answer 1

( x - 2 ) ³ - ( x + 1 ) ³ + 9x ( x + 1 ) - 9 = 0
=> \(x^3-6x^2+12x-8-\left(x^3+3x^2+3x+1\right)+9x^2+9x-9=0\)
=> \(x^3-6x^2+12x-8-x^3-3x^2-3x-1+9x^2+9x-9=0\)
=> \(18x-18=0\)
=>         \(18x=0+18\)
=>         \(18x=18\)
=>             \(x=1\)