Question

Tìm x biết

Answer 1

\(\left(x^2-5\right)\left(x+3\right)+x\left(x+4\right)\left(1-x\right)=7\)

\(\Leftrightarrow x^3+3x^2-5x-15-x^3-3x^2+4x=7\)

\(\Leftrightarrow x=-22\)

Answer 2

\(\left(x^2-5\right)\left(x+3\right)+x\left(x+4\right)\left(1-x\right)=7\)

\(\Leftrightarrow x^3+3x^2-5x-15-x\left(x-x^2+4-4x\right)=7\)

\(\Leftrightarrow x^3+3x^2-5x-15-x\left(-x^2-3x+4\right)=7\)

\(\Leftrightarrow x^3+3x^2-5x-15+x^3+3x^2-4x-7=0\)

\(\Leftrightarrow2x^3+6x^2-9x-22=0\)

\(\Leftrightarrow x-2=0\)

hay x=2