Question

a) (x-1)^3-x(x+1)^2=5x(2-x)-11(x+2)

b) (x-3)(x+4)-2(3x-2)=(x-4)^2

Answer 1

a, Tính ra thôi:\(\left(x-1\right)^3-x\left(x+1\right)^2=5x\left(2-x\right)-11\left(x+2\right)\)

<=> \(x^3-3x^2+3x-1-x\left(x^2+2x+1\right)=10x-5x^2-11x-22\)

<=>\(-5x^2+2x-1=-x-5x^2-22\)

<=>\(-5x^2+5x^2+2x+x=-22+1\)

<=> 3x=-21

=>x=-7.

b, \(\left(x-3\right)\left(x+4\right)-2\left(3x-2\right)=\left(x-4\right)^2\)

<=> \(x^2+4x-3x-12-6x+4=x^2-2.4x+4^2\)

<=>\(x^2-5x-8=x^2-8x+16\)

<=> \(x^2-x^2-5x+8x=16+8\)

<=> 3x=24

=> x=8