Question

[Nguyễn Hải Đăng]

a) căn 110 + căn 70 / căn 22 + căn 14 b) căn 42 - 6 / căn 21 - căn 18

c) ( a - b) . căn a^2 - b^2 / ( a - b )^2 ( a > 0 b < 0 và a khác b )

Answer 1

[Huyen Trang]

a) \(\frac{\sqrt{110}+\sqrt{70}}{\sqrt{22}+\sqrt{14}}=\frac{\left(\sqrt{11}+\sqrt{7}\right)\sqrt{10}}{\left(\sqrt{11}+\sqrt{7}\right)\sqrt{2}}=\sqrt{5}\)

b) \(\frac{\sqrt{42}-6}{\sqrt{21}-\sqrt{18}}=\frac{\sqrt{42}-\sqrt{36}}{\sqrt{21}-\sqrt{18}}\)

\(=\frac{\left(\sqrt{7}-\sqrt{6}\right)\sqrt{6}}{\left(\sqrt{7}-\sqrt{6}\right)\sqrt{3}}=\sqrt{2}\)

c) \(\frac{\left(a-b\right)\sqrt{a^2-b^2}}{\left(a-b\right)^2}\)

\(=\frac{\sqrt{\left(a-b\right)\left(a+b\right)}}{a-b}\)