\(\left(2x+1\right)^2=\dfrac{25}{4}\)
\(\Rightarrow\left(2x+1\right)^2=\left(\pm\dfrac{5}{2}\right)^2\)
+) \(2x+1=\dfrac{5}{2}\)
\(\Rightarrow2x=\dfrac{3}{2}\)
\(\Rightarrow x=\dfrac{3}{4}\)
+) \(2x+1=-\dfrac{5}{2}\)
\(\Rightarrow2x=-\dfrac{7}{2}\)
\(\Rightarrow x=-\dfrac{7}{4}\)
(2x + 1)² = 25/4
2x + 1 = 5/2 hoặc 2x + 1 = -5/2
*) 2x + 1 = 5/2
2x = 5/2 - 1
2x = 3/2
x = 3/2 : 2
x = 3/4
*) 2x + 1 = -5/2
2x = -5/2 - 1
2x = -7/2
x = -7/2 : 2
x = -7/4
Vậy x = -7/4; x = 3/4
`(2x+1)^2 =25/4`
`=> (2x+1)^2 =(+- 5/2)^2`
\(\Rightarrow\left[{}\begin{matrix}2x+1=\dfrac{5}{2}\\2x+1=-\dfrac{5}{2}\end{matrix}\right.\\ \Rightarrow\left[{}\begin{matrix}2x=\dfrac{3}{2}\\2x=-\dfrac{7}{2}\end{matrix}\right.\\\Rightarrow\left[{}\begin{matrix}x=\dfrac{3}{4}\\x=-\dfrac{7}{4}\end{matrix}\right.\)
