Đáp án:
`a) `\(\left[ \begin{array}{l}x=\frac{7}{4}\\x=\frac{-3}{4}\end{array} \right.\)
`b)` \(\left[ \begin{array}{l}x=0\\x=-3\\x=2\end{array} \right.\)
Giải thích các bước giải:
`a) (4x-2)^2-25=0`
`<=> (4x-2)^2-5^2=0`
`<=> (4x-2-5)(4x-2+5)=0`
`<=> (4x-7)(4x+3)=0`
`<=>`\(\left[ \begin{array}{l}4x-7=0\\4x+3=0\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}4x=7\\4x=-3\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}x=\frac{7}{4}\\x=\frac{-3}{4}\end{array} \right.\)
`b) x^3+27+(x+3)(x-9)=0`
`<=> (x+3)(x^2-3x+9)+(x+3)(x-9)=0`
`<=> (x+3)(x^2-3x+9+x-9)=0`
`<=> (x+3)(x^2-2x)=0`
`<=> x(x+3)(x-2)=0`
`<=>`\(\left[ \begin{array}{l}x=0\\x+3=0\\x-2=0\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}x=0\\x=-3\\x=2\end{array} \right.\)
