Question

Tìm x
a) \(\left(x+1\right)^2+2\left(x+2\right)^2=3x\left(x-1\right)+15\)

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

Answer 1

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

\(\Leftrightarrow x^2+2x+1+2\left(x^2+4x+4\right)=3x^2-3x+15\)

\(\Leftrightarrow x^2+2x+1+2x^2+8x+8=3x^2-3x+15\)

\(\Leftrightarrow3x^2+10x+9=3x^2-3x+15\)

\(\Leftrightarrow13x=6\Leftrightarrow x=\frac{6}{13}\)

Answer 2

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

\(\Leftrightarrow x^2+4x+4=x^2-2x-3+6\)

\(\Leftrightarrow6x=-1\Leftrightarrow x=\frac{-1}{6}\)