Question

Tìm x biết

(x³ - 27) - (3 - x)(6x + 9) = 0

Answer 1

=>(x-3)(x^2+3x+9)+(x-3)(6x+9)=0

=>(x-3)(x^2+9x+18)=0

=>(x-3)(x+3)(x+6)=0

hay \(x\in\left\{3;-3;-6\right\}\)

Answer 2

(x^3-27)-(3-x)(6x+9)=0

=>(x-3)(x^2+3x+9)-(3-x)(6x+9)=0

=>(x-3)(x^2+9x+18)=0

=>(x-3)(x+3)(X+6)=0

=>x=3;-3;-6