rút gọn biểu thức sau
3 .16 /12.9
11.5 -11.7 /11
6 /11 - 6/9 +6 /5 /21/11- 21/9+21/5
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\(\dfrac{\left(-6\right).11}{\left(-11\right).\left(-8\right)}=\dfrac{\left(-3\right).2.11}{11.2.4}=-\dfrac{3}{4}\)
\(\dfrac{21.\left(-5\right)}{25.\left(-7\right)}=\dfrac{\left(-3\right).\left(-7\right).\left(-5\right)}{\left(-5\right).\left(-5\right).\left(-7\right)}=\dfrac{3}{5}\)
\(\dfrac{32.9.11}{12.24.22}=\dfrac{4.4.2.3.3.11}{3.4.4.2.3.11.2}=\dfrac{4^2.2.3^2.11}{3^2.4^2.2^2.11}=\dfrac{1}{2}\)
\(\dfrac{\left(-6\right).11}{\left(-11\right).\left(-8\right)}\)=\(\dfrac{-3}{4}\)
\(\dfrac{21.\left(-5\right)}{25.\left(-7\right)}\)=\(\dfrac{2}{5}\)
\(\dfrac{32.9.11}{12.24.22}\)=\(\dfrac{1}{2}\)
1) \(\sqrt{6+4\sqrt{2}}-\sqrt{11-6\sqrt{2}}\)
\(=\sqrt{2^2+2\cdot2\cdot\sqrt{2}+\left(\sqrt{2}\right)^2}-\sqrt{3^2-2\cdot3\cdot\sqrt{2}+\left(\sqrt{2}\right)^2}\)
\(=\sqrt{\left(2+\sqrt{2}\right)^2}-\sqrt{\left(3-\sqrt{2}\right)^2}\)
\(=\left|2+\sqrt{2}\right|-\left|3-\sqrt{2}\right|\)
\(=2+\sqrt{2}-3+\sqrt{2}\)
\(=2\sqrt{2}-1\)
2) \(\sqrt{21-4\sqrt{5}}+\sqrt{21+4\sqrt{5}}\)
\(=\sqrt{20-4\sqrt{5}+1}+\sqrt{20+4\sqrt{5}+1}\)
\(=\sqrt{\left(2\sqrt{5}\right)^2-2\sqrt{5}\cdot2\cdot1+1^2}+\sqrt{\left(2\sqrt{5}\right)^2+2\sqrt{5}\cdot2\cdot1-1^2}\)
\(=\sqrt{\left(2\sqrt{5}-1\right)^2}+\sqrt{\left(2\sqrt{5}+1\right)^2}\)
\(=\left|2\sqrt{5}-1\right|+\left|2\sqrt{5}+1\right|\)
\(=2\sqrt{5}-1+2\sqrt{5}+1\)
\(=4\sqrt{5}\)
a: \(=\left(\sqrt{3}-2\right)\cdot\sqrt{\left(2+\sqrt{3}\right)^2}\)
\(=\left(\sqrt{3}-2\right)\left(\sqrt{3}+2\right)\)
=3-4=-1
b: \(=\sqrt{6+4\sqrt{2}}-\sqrt{11-2\sqrt{18}}\)
\(=\sqrt{\left(2+\sqrt{2}\right)^2}-\sqrt{\left(3-\sqrt{2}\right)^2}\)
\(=2+\sqrt{2}-3+\sqrt{2}=2\sqrt{2}-1\)
c: \(=\sqrt{\left(2\sqrt{5}-1\right)^2}+\sqrt{\left(2\sqrt{5}+1\right)^2}\)
\(=2\sqrt{5}-1+2\sqrt{5}+1\)
\(=4\sqrt{5}\)
a: =1/4+1/4=2/4=1/2
b: =3/5+3/5=6/5
c: =5/9+7/9=12/9=4/3