Bài 1:
a) \(2\sqrt{25}+3\sqrt{4}=2.5+3.2=16\)
b)\(\left\{{}\begin{matrix}a+b=-2\\3a+b=4\end{matrix}\right.\)
c)\(A=\left(\dfrac{x-2\sqrt{x}+2\sqrt{x}+4}{\left(\sqrt{x}+2\right)\left(\sqrt{x}-2\right)}\right).\dfrac{\sqrt{x}+2}{x+4}\)
\(A=\dfrac{1}{\sqrt{x}-2}\)