Question

\((x+2)(1-4x^2)=x^2+4x+4\)

Giải pt

Answer 1

\(\Leftrightarrow\left(x+2\right)\left(1-4x^2\right)-\left(x+2\right)^2=0\)

\(\Leftrightarrow\left(x+2\right)\left(1-4x^2-x-2\right)=0\)

\(\Leftrightarrow x+2=0\)

hay x=-2

Answer 2

\(\left(x+2\right)\left(1-4x^2\right)=x^2+4x+4\\ \Leftrightarrow\left(x+2\right)\left(1-4x^2\right)-\left(x+2\right)^2\\ \Leftrightarrow\left(x+2\right)\left(1-4x^2-x-2\right)=0\\ \Leftrightarrow\left(x+2\right)\left(-4x^2-x-1\right)=0\\ \Leftrightarrow\left(x+2\right)\left(4x^2+x+1\right)=0\\ \Leftrightarrow x+2=0\left(vì.4x^2+x+1>0\right)\\ \Leftrightarrow x=-2\)