Bài 1:
a) 4x-\(\sqrt{9x^2-12x+4}\)
= 4x-\(\sqrt{\left(3x-2\right)^2}\)
= 4x-\(|3x-2|\)
= 4x-3x+2
= x+2
b) Thay x=\(\dfrac{2}{7}\)vào biểu thức A, ta có:
A= \(\dfrac{2}{7}+\dfrac{1}{2}\)= \(\dfrac{11}{14}\)
Bài 2:
a) \(\sqrt{x^2+2x+1}=\sqrt{x+1}\)
\(\Leftrightarrow\)\(\left(\sqrt{x^2+2x+1}\right)^2=\left(\sqrt{x+1}\right)^2\)
\(\Leftrightarrow\)x2+2x+1=x+1
\(\Leftrightarrow\)x2+2x+1-x-1=0
\(\Leftrightarrow\)x2-x=0
\(\Leftrightarrow\)x(x-1)=0
\(\Leftrightarrow\)\(\left[{}\begin{matrix}x=0\\x-1=0\end{matrix}\right.\)
\(\Leftrightarrow\)\(\left[{}\begin{matrix}x=0\\x=1\end{matrix}\right.\)
