Question

Tìm x, biết:

\(\left(x-2\right)^3-\left(x-3\right)\left(x^2+3x+9\right)+6\left(x+1\right)=15\)

Answer 1

Bài này mà để vào câu hỏi hay clone con ạ :))

Answer 2

\(\left(x-2\right)^3-\left(x-3\right)\left(x^2+3x+9\right)+6\left(x+1\right)=15\)

\(\Rightarrow\left(x-2\right)^3-x^3+27+6x+6=15\)

\(\Rightarrow\left(x-2-x\right)\left[\left(x-2\right)^2+\left(x-2\right)x+x^2\right]+33+6x\) = 15

\(\Rightarrow-2\left(x^2-4x+4+x^2-2x+x^2\right)+33+6x=15\)

\(\Rightarrow-2\left(3x^2-6x+4\right)+33+6x=15\)

\(\Rightarrow-6x^2+12x-8+33+6x=15\)

\(\Rightarrow-6x^2+18x+25=15\)

\(\Rightarrow-6x^2+18x+10=0\)

\(\Rightarrow2\left(-3x^2+9x+5\right)=0\)