Question

tìm x biết:(x+2).(x^2-2x+4)-x.(x^2-2)=15

Answer 1

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

\(\Leftrightarrow x^3+8-x^3+2x=15\)

\(\Leftrightarrow2x+8=15\)

\(\Leftrightarrow2x=15-8=7\)

\(\Leftrightarrow x=\frac{7}{2}\)

Answer 2

\(\left(x+2\right)\left(x^2-2x+4\right)-x.\left(x^2-2\right)=15\)