a, Ta có : \(x-\frac{2.\sqrt{x}.1}{2}+\frac{1}{4}-\frac{25}{4}\)
\(=\left(x-\frac{1}{2}\right)^2-\left(\frac{5}{2}\right)^2\)
\(=\left(x-\frac{1}{2}-\frac{5}{2}\right)\left(x-\frac{1}{2}+\frac{5}{2}\right)=\left(x-3\right)\left(x+2\right)\)
b, Ta có : \(\left(\sqrt{a}\right)^2-2\sqrt{a}+1=\left(\sqrt{a}-1\right)^2\)
c, Ta có : \(\left(\sqrt{x}\right)^2-2.2\sqrt{x}+2^2=\left(\sqrt{x}-2\right)^2\)