Question

Rút gọn: \(B=\left(\dfrac{1}{2-\sqrt{a}}-\dfrac{1}{2+\sqrt{a}}\right)\left(\dfrac{2}{\sqrt{a}}+1\right)\) với a khác 4

Answer 1

đkxd: \(a>0;a\ne4\)

B \(=\left(\dfrac{2+\sqrt{a}-\left(2-\sqrt{a}\right)}{\left(2-\sqrt{a}\right)\left(2+\sqrt{a}\right)}\right)\left(\dfrac{2+\sqrt{a}}{\sqrt{a}}\right)\)

B \(=\left(\dfrac{2+\sqrt{a}-2+\sqrt{a}}{\left(2-\sqrt{a}\right)\left(2+\sqrt{a}\right)}\right)\left(\dfrac{2+\sqrt{a}}{\sqrt{a}}\right)\)

B \(=\dfrac{2\sqrt{a}\left(2+\sqrt{a}\right)}{\left(2-\sqrt{a}\right)\left(2+\sqrt{a}\right)\sqrt{a}}=\dfrac{2}{2-\sqrt{a}}\)