Gíup mình thật đầy đủ,mình cảm ơn
Bài 4:
a: Ta có: \(\sqrt{-x^2+x+4}=x-3\)
\(\Leftrightarrow-x^2+x+4=x^2-6x+9\)
\(\Leftrightarrow-2x^2+7x-5=0\)
\(\Leftrightarrow\left(x-1\right)\left(2x-5\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=1\left(loại\right)\\x=\dfrac{5}{2}\left(loại\right)\end{matrix}\right.\)
b: Ta có: \(\sqrt{x-3}-2\sqrt{x^2-9}=0\)
\(\Leftrightarrow\sqrt{x-3}\left(1-2\sqrt{x+3}\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x-3=0\\x+3=\dfrac{1}{4}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=3\\x=\dfrac{1}{4}-3=\dfrac{-11}{4}\end{matrix}\right.\)
Bài 3:
c: Ta có: \(P=\dfrac{a+4\sqrt{a}+4}{\sqrt{a}+2}-\dfrac{a-4}{\sqrt{a}-2}\)
\(=\sqrt{a}+2-\sqrt{a}-2\)
=0
