Đáp án:
`a)x=-6/5` hoặc `x=-9/5`
`b)x=11/3`
`c)x=-1/8`
`d)x=±5`
Giải thích các bước giải:
`a)(2x+3)²=9/25`
`→(2x+3)²=(±3/5)^2`
`→`\(\left[ \begin{array}{l}2x+3=\dfrac{3}{5}\\2x+3=-\dfrac{3}{5}\end{array} \right.\)
`→`\(\left[ \begin{array}{l}2x=\dfrac{3}{5}-3\\2x=-\dfrac{3}{5}-3\end{array} \right.\)
`→`\(\left[ \begin{array}{l}2x=-\dfrac{12}{5}\\2x=-\dfrac{18}{5}\end{array} \right.\)
`→`\(\left[ \begin{array}{l}x=(-\dfrac{12}{5}):2\\x=(-\dfrac{18}{5}):2\end{array} \right.\)
`→`\(\left[ \begin{array}{l}x=-\dfrac{6}{5}\\x=-\dfrac{9}{5}\end{array} \right.\)
Vậy `x=-6/5` hoặc `x=-9/5`
`b)(3-x)³=-8/27`
`→(3-x)³=(-2/3)^3`
`→3-x=-2/3`
`→x=3-(-2/3)`
`→x=3+2/3`
`→x=9/3+2/3`
`→x=11/3`
Vậy `x=11/3`
`c)x+1/2=3/8`
`→x=3/8-1/2`
`→x=3/8-4/8`
`→x=-1/8`
Vậy `x=-1/8`
`d)x^20=25.x^18`
`→x^20:x^18=25`
`→x²=25`
`→x²=5²`
`→x=±5`
Vậy `x=±5`
