Đáp án:
`d)S={5/2;25/8}`
Giải thích các bước giải:
`d)4x²-25-9(2x-5)²=0`
`⇔(4x²-25)-9(2x-5)²=0`
`⇔[(2x)²-5²]-9(2x-5)²=0`
`⇔(2x+5)(2x-5)-9(2x-5)²=0`
`⇔(2x-5)[2x+5-9(2x-5)]=0`
`⇔(2x-5)(2x+5-18x+45)=0`
`⇔(2x-5)(50-16x)=0`
`⇔`\(\left[ \begin{array}{l}2x-5=0\\50-16x=0\end{array} \right.\)
`⇔`\(\left[ \begin{array}{l}2x=5\\16x=50\end{array} \right.\)
`⇔`\(\left[ \begin{array}{l}x=\dfrac{5}{2}\\x=\dfrac{25}{8}\end{array} \right.\)
Vậy `S={5/2;25/8}`
