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a, Ta có: \(\sqrt{36}=6\)
Vì \(36>35\Rightarrow\sqrt{36}>\sqrt{35}\) hay \(6>\sqrt{35}\)
Câu a)
\(A=\sqrt{20+1}+\sqrt{40+2}+\sqrt{60+3}\)
\(=\sqrt{1\left(20+1\right)}+\sqrt{2\left(20+1\right)}+\sqrt{3\left(20+1\right)}\)
\(=\sqrt{20+1}\left(\sqrt{1}+\sqrt{2}+\sqrt{3}\right)\)
\(B=\sqrt{1}+\sqrt{2}+\sqrt{3}+\sqrt{20}+\sqrt{40}+\sqrt{60}\)
\(=1\left(\sqrt{1}+\sqrt{2}+\sqrt{3}\right)+\left(\sqrt{1}\cdot\sqrt{20}+\sqrt{2}\cdot\sqrt{20}+\sqrt{3}\cdot\sqrt{20}\right)\)
\(=\sqrt{1}\left(\sqrt{1}+\sqrt{2}+\sqrt{3}\right)+\sqrt{20}\left(\sqrt{1}+\sqrt{2}+\sqrt{3}\right)\)
\(=\left(\sqrt{20}+\sqrt{1}\right)\left(\sqrt{1}+\sqrt{2}+\sqrt{3}\right)\)
Ta thấy: \(\hept{\begin{cases}\left(\sqrt{20+1}\right)^2=20+1\\\left(\sqrt{20}+\sqrt{1}\right)^2=20+1+2\sqrt{20}\end{cases}}\)
\(\Rightarrow\left(\sqrt{20+1}\right)^2< \left(\sqrt{20}+\sqrt{1}\right)^2\Rightarrow\sqrt{20+1}< \sqrt{20}+\sqrt{1}\)
Vậy A < B.
A= ( \(\sqrt{1}\)+\(\sqrt{2}\)+\(\sqrt{3}\) ) + (\(\sqrt{20}\) + \(\sqrt{40}\) + \(\sqrt{60}\))
= (1+1,4+1,7)+(4,4+6,3+7,7)
= 4,1+18,4
=22,5
=1-2+3-4+5-6+...+19-20
=-1-1-1-1-1-1-...-1
20 so-1
=-1.20=-20
\(a,\sqrt{81}=9\)
\(b.\sqrt{8100}=90\)
\(c,\sqrt{64}=8\)
\(d,\sqrt{25}=5\)
\(e,\sqrt{0,64}=0,8\)
\(f,\sqrt{10000}=100\)
\(g,\sqrt{0,01}=0,1\)
\(h,\sqrt{\frac{49}{100}}=\frac{7}{10}\)
\(i,\sqrt{\frac{0,09}{121}}=\frac{0,3}{11}\)
\(j,\sqrt{\frac{4}{25}}=\frac{2}{5}\)
~Study well~
#JDW
a) 9
b) 90
c) 8
d) 5
e) 0,8
f) 100
g) 0,1
h) \(\frac{7}{10}\)
i) \(\frac{0,3}{11}\)
j) 0,4.
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