a: Ta có: \(A=\sqrt{112}-7\cdot\sqrt{\dfrac{1}{7}}-14\cdot\sqrt{\dfrac{1}{28}}-\dfrac{21}{\sqrt{7}}\)
\(=4\sqrt{7}-\sqrt{7}-\sqrt{7}-3\sqrt{7}\)
\(=-\sqrt{7}\)
b: Ta có: \(B=3\sqrt{2}\left(4-\sqrt{2}\right)+3\left(1-2\sqrt{2}\right)^2\)
\(=12\sqrt{2}-6+3\left(9-4\sqrt{2}\right)\)
\(=12\sqrt{2}-6+27-12\sqrt{2}\)
=21
c: Ta có: \(C=2\sqrt{27}+5\sqrt{12}-3\sqrt{48}\)
\(=6\sqrt{3}+10\sqrt{3}-12\sqrt{3}\)
\(=4\sqrt{3}\)
d: Ta có: \(D=\sqrt{147}+\sqrt{54}-4\sqrt{27}\)
\(=7\sqrt{3}+3\sqrt{6}-12\sqrt{3}\)
\(=3\sqrt{6}-5\sqrt{3}\)
e: Ta có: \(E=\left(\sqrt{15}-2\sqrt{3}\right)^2+12\sqrt{5}\)
\(=27-12\sqrt{5}+12\sqrt{5}\)
=27
f: Ta có: \(F=3\sqrt{50}-7\sqrt{8}+12\sqrt{18}\)
\(=12\sqrt{2}-14\sqrt{2}+36\sqrt{2}\)
\(=34\sqrt{2}\)
g: Ta có: \(G=2\sqrt{80}-2\sqrt{245}+2\sqrt{180}\)
\(=8\sqrt{5}-14\sqrt{5}+12\sqrt{5}\)
\(=6\sqrt{5}\)
h: Ta có: \(H=\sqrt{28}-4\sqrt{63}+7\sqrt{112}\)
\(=2\sqrt{7}-12\sqrt{7}+28\sqrt{7}\)
\(=18\sqrt{7}\)
m: Ta có: \(M=\sqrt{20}-2\sqrt{10}+\sqrt{45}\)
\(=2\sqrt{5}+3\sqrt{5}-2\sqrt{10}\)
\(=5\sqrt{5}-2\sqrt{10}\)
n: Ta có: \(N=2\sqrt{12}-\sqrt{48}+3\sqrt{27}-\sqrt{108}\)
\(=4\sqrt{3}-4\sqrt{3}+9\sqrt{3}-6\sqrt{3}\)
\(=3\sqrt{3}\)
