Đáp án:
`a) (x-5)^2+x^2-25=0`
`<=> (x-5)^2+(x-5)(x+5)=0`
`<=> (x-5)(x-5+x+5)=0`
`<=> 2x(x-5)=0`
`<=>`\(\left[ \begin{array}{l}x=0\\x-5=0\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}x=0\\x=5\end{array} \right.\)
`b) 81/64x^3-25x=0`
`<=> x(81/64x^2-25)=0`
`<=> x(9/8x-5)(9/8x+5)=0`
`<=>`\(\left[ \begin{array}{l}x=0\\\dfrac{9}{8}x-5=0\\\dfrac{9}{8}x+5=0\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}x=0\\x=\dfrac{40}{9}\\x=\dfrac{-40}{9}\end{array} \right.\)
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