Đáp án-Giải thích các bước giải:
` d)(2x+7)^2=9(x+2)^2`
`<=>(2x+7)^2-9(x+2)^2=0`
`<=>[2x+7-3(x+2)][2x+7+3(x+2)]=0`
`<=>(2x+7-3x-6)(2x+7+3x+6)=0`
`<=>(1-x)(5x+13)=0`
`<=>`\(\left[ \begin{array}{l}1-x=0\\5x+13=0\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}x=1\\x=\dfrac{-13}{5}\end{array} \right.\)
Vậy `S={1;-13/5}`
`e)(5x^2-2x+10)^2=(3x^2+10x-8)^2`
`<=>(5x^2-2x+10)^2-(3x^2+10x-8)^2=0`
`<=>(5x^2-2x+10-3x^2-10x+8)(5x^2-2x+10+3x^2+10x-8)=0`
`<=>(2x^2-12x+18)(8x^2+8x+2)=0`
`<=>2(x^2-6x+9).2(4x^2+4x+1)=0`
`<=>8(x-3)^2(2x+1)^2=0`
`<=>`\(\left[ \begin{array}{l}x-3=0\\2x+1=0\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}x=3\\x=-\dfrac{1}{2}\end{array} \right.\)
Vậy `S={1;-1/2}`
