Question

[Mai Quốc Việt]

Tìm x biết : 

 (x +1)^3 - (x - 1)^3 - 6 (x - 1)^2 = -10

Answer 1

[Võ Đông Anh Tuấn]

\(\left(x+1\right)^3-\left(x-1\right)^3-6\left(x-1\right)^2=-10\)

\(\Leftrightarrow\left[\left(x+1\right)\left(x-1\right)\right]\left[\left(x+1\right)^2+\left(x+1\right)\left(x-1\right)+\left(x-1\right)^2\right]-6\left(x^2-2x+1\right)=-10\)

\(\Leftrightarrow6x^2+2-6x^2+12x-6=-10\)

\(\Leftrightarrow12x=-6\)

\(\Leftrightarrow x=-6:12\)

\(\Leftrightarrow x=-0,5\)

Answer 2

[phan thị minh anh]

(x^3+3x^2+3x+1 )-(x^3 -3x^2 +3x-1)-6(x^2 -2x+1)=-10

6x^2 +2-6x^2 +12x-6=-10

12x-4=-10

12x=-6

x=-1/2