Question

Giải các phương trình sau 
a) (3-2x)^2 + 4x^2 - 9 = 0
b) (x+2)^3 - 9(x+2) = 0

Answer 1

a) \(\left(3-2x\right)^2+4x^2-9=0\)

\(\Leftrightarrow9-12x+4x^2+4x^2-9=0\)

\(\Leftrightarrow12x=0\)

\(\Leftrightarrow x=0\)

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

\(\Leftrightarrow\left(x+2\right)\left[\left(x+2\right)^2-9\right]=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x+2=0\\\left(x+2\right)^2-9=0\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=-2\\\left(x+2\right)^2=9\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=-2\\x+2=3\\x+2=-3\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=-2\\x=1\\x=-5\end{matrix}\right.\)