RÚT GỌN CÁC BIỂU THỨC SAU :
a ] \(\dfrac{1}{4}\)\(\sqrt{180}\) + \(\sqrt{20}\)- \(\sqrt{45}\) + 5
b] \(\sqrt[3]{\dfrac{1}{3}}\) +\(\dfrac{1}{4}\)\(\sqrt{48}\) - \(2\sqrt{3}\)
c] \(\sqrt{2a}\) - \(\sqrt{18}a^3\) +\(\sqrt[4]{\dfrac{a}{2}}\)
d]\(\sqrt{\dfrac{a}{1+2b+b^2}}\) . \(\sqrt{\dfrac{4a+8ab+4ab^2}{225}}\)
a) ...= \(\dfrac{1}{4}\).\(6\sqrt{5}\) +\(2\sqrt{5}\) - \(3\sqrt{5}\) +5
= \(\dfrac{3}{2}\sqrt{5}\) -\(\sqrt{5}\) +5
=5 - \(\dfrac{1}{2}\sqrt{5}\)
d) ...= \(\sqrt{\dfrac{a}{\left(1+b\right)^2}}\) . \(\sqrt{\dfrac{4a\left(1+b\right)^2}{15^2}}\)
= \(\sqrt{\dfrac{4a^2\left(1+b\right)^2}{\left(1+b\right)^2.15^2}}\) = \(\sqrt{\dfrac{4a^2}{15^2}}\)= \(\dfrac{2a}{15}\)
