Bài 1 :
`a) (2x+1)^2=9`
` (2x+1)^2=3^2=(-3)^2`
`=>`$\left[\begin{matrix} 2x+1=3\\ 2x+1=-3\end{matrix}\right.$
`=>`$\left[\begin{matrix} 2x=4\\ 2x=-2\end{matrix}\right.$
`=>`$\left[\begin{matrix} x=2\\ x=-1\end{matrix}\right.$
`b)(3x-1)^2=81 `
` (3x-1)^2 =9^2=(-9)^2`
`=>`$\left[\begin{matrix} 3x-1=9\\ 3x-1=-9\end{matrix}\right.$
`=>`$\left[\begin{matrix} 3x=10\\ 3x=-8\end{matrix}\right.$
`=>`$\left[\begin{matrix} x=\dfrac{10}{3}\\ x=\dfrac{-8}{3}\end{matrix}\right.$
`c) (x-1/2)^2=4/9`
` (x-1/2)^1=(2/3)^2=(-2/3)^2`
`=>`$\left[\begin{matrix} x-\dfrac{1}{2}=\dfrac{2}{3}\\ x-\dfrac{1}{2}=\dfrac{-2}{3}\end{matrix}\right.$
`=>`$\left[\begin{matrix} x=\dfrac{7}{6}\\ x=\dfrac{-1}{6}\end{matrix}\right.$
`d)(2x-5)^4=16`
` (2x-5)^4=2^4=(-2)^4`
`=>`$\left[\begin{matrix} 2x-5=2\\ 2x-5=-2\end{matrix}\right.$
`=>`$\left[\begin{matrix} 2x=7\\ 2x=3\end{matrix}\right.$
`=>`$\left[\begin{matrix} x=\dfrac{7}{2}\\ x=\dfrac{3}{2} \end{matrix}\right.$
`e)(2x+5)^4=81`
` (2x+5)^4=3^4=(-3)^4`
`=>`$\left[\begin{matrix} 2x+5=3\\ 2x+5=-3\end{matrix}\right.$
`=>`$\left[\begin{matrix} 2x=-2\\ 2x=-8\end{matrix}\right.$
`=>`$\left[\begin{matrix} x=-1\\ x=-4\end{matrix}\right.$
`f)(x+1)^2=1^3+2^3+3^3+4^3`
` (x+1)^2=1+8+27+64`
` (x+1)^2=100`
` (x+1)^2=10^2=(-10)^2`
`=>`$\left[\begin{matrix} x+1=10\\ x+1=-10\end{matrix}\right.$
`=>`$\left[\begin{matrix} x=9\\ x=-11\end{matrix}\right.$
`g)(x-2)^2=1+3+5+......+99`
` (x-2)^2=2500`
` (x-2)^2=50^2=(-50)^2`
`=>`$\left[\begin{matrix} x-2=50\\ x-2=-50\end{matrix}\right.$
`=>`$\left[\begin{matrix} x=52\\ x=-48\end{matrix}\right.$
$\text{Xin hay nhất }$
