So sánh
\(3\sqrt{3}\)và \(\sqrt{12}\)
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a: \(1< \sqrt{2}\)
nên \(2< \sqrt{2}+1\)
b: \(2\sqrt{31}=\sqrt{124}\)
\(10=\sqrt{100}\)
mà 124>100
nên \(2\sqrt{31}>10\)
c: \(-3\sqrt{11}=-\sqrt{99}\)
\(-\sqrt{12}=-\sqrt{12}\)
mà 99>12
nên \(-3\sqrt{11}< -\sqrt{12}\)
Lời giải:
\(2\sqrt{12}>2\sqrt{9}=2.3=6>3\)
\(\sqrt{6}> \sqrt{5}\)
\(\Rightarrow 2\sqrt{12}+\sqrt{6}> 3+\sqrt{5}\)
a)
Có: \(2>1>0\)
\(\Rightarrow\sqrt{2}>1\Rightarrow1+\sqrt{2}>1+1\\ \Leftrightarrow1+\sqrt{2}>2\)
b) Có: \(0< \sqrt{3}< 3\)
\(\Rightarrow3+1>\sqrt{3}+1\\ \Rightarrow4>\sqrt{3}+1\)
c) Có: \(0< \sqrt{11}< \sqrt{25}\left(0< 11< 25\right)\)
\(\Rightarrow\sqrt{11}< 5\\ \Rightarrow-2\sqrt{11}>-2.5=-10\left(-2< 0\right)\)
d) Có: \(0< \sqrt{11}< \sqrt{16}=4\left(do.0< 11< 16\right)\)
\(\Rightarrow3\sqrt{11}< 3.4\\ \Leftrightarrow3\sqrt{11}< 12\)
a: 2=1+1<1+căn 2
b: 4=1+3>1+căn 3
c: -2căn 11=-căn 44
-10=-căn 100
mà 44<100
nên -2 căn 11>-10
d: 12=3*4=3*căn 16>3*căn 11
Ta có: \(12>9\)
\(6\sqrt{3}>4\sqrt{5}\)
Do đó: \(12+6\sqrt{3}>9+4\sqrt{5}\)
\(\Leftrightarrow\sqrt{12+6\sqrt{3}}>\sqrt{9+4\sqrt{5}}\)
a) Ta có:
\(2=1+1=1+\sqrt{1}\)
Mà: \(1< 2\Rightarrow\sqrt{1}< \sqrt{2}\)
\(\Rightarrow1+\sqrt{1}< \sqrt{2}+1\)
\(\Rightarrow2< \sqrt{2}+1\)
b) Ta có:
\(1=2-1=\sqrt{4}-1\)
Mà: \(4>3\Rightarrow\sqrt{4}>\sqrt{3}\)
\(\Rightarrow\sqrt{4}-1>\sqrt{3}-1\)
\(\Rightarrow1>\sqrt{3}-1\)
c) Ta có:
\(10=2\cdot5=2\sqrt{25}\)
Mà: \(25< 31\Rightarrow\sqrt{25}< \sqrt{31}\)
\(\Rightarrow2\sqrt{25}< 2\sqrt{31}\)
\(\Rightarrow10< 2\sqrt{31}\)
d) Ta có:
\(-12=-3\cdot4=-3\sqrt{16}\)
Mà: \(16>11\Rightarrow\sqrt{16}>\sqrt{11}\)
\(\Rightarrow-3\sqrt{16}< -3\sqrt{11}\)
\(\Rightarrow-12< -3\sqrt{11}\)
\(A=\left(\sqrt{1}+\sqrt{2}+\sqrt{3}+\sqrt{4}\right)+\left(\sqrt{5}+\sqrt{6}+\sqrt{7}+\sqrt{8}+\sqrt{9}\right)+\left(\sqrt{10}+\sqrt{11}+\sqrt{12}\right)\)
Ta có:
\(\sqrt{1}+\sqrt{2}+\sqrt{3}+\sqrt{4}>1+\sqrt{1}+\sqrt{1}+\sqrt{1}+2=5\)
\(\sqrt{5}+\sqrt{6}+\sqrt{7}+\sqrt{8}+\sqrt{9}>\sqrt{5}+\sqrt{5}+\sqrt{5}+\sqrt{5}+\sqrt{5}=5\sqrt{5}\)
\(\sqrt{10}+\sqrt{11}+\sqrt{12}>\sqrt{9}+\sqrt{9}+\sqrt{9}=9\)
=> \(A>5+5\sqrt{5}+9=14+5\sqrt{5}>12+5\sqrt{5}\)
Vậy...
a: \(\sqrt[3]{-8}\cdot\sqrt[3]{27}=-2\cdot3=-6\)
\(\sqrt[3]{\left(-8\right)\cdot27}=\sqrt[3]{-216}=-6\)
Do đó: \(\sqrt[3]{-8}\cdot\sqrt[3]{27}=\sqrt[3]{\left(-8\right)\cdot27}\)
b: \(\dfrac{\sqrt[3]{-8}}{\sqrt[3]{27}}=-\dfrac{2}{3}\)
\(\sqrt[3]{-\dfrac{8}{27}}=-\dfrac{2}{3}\)
Do đó: \(\dfrac{\sqrt[3]{-8}}{\sqrt[3]{27}}=\sqrt[3]{-\dfrac{8}{27}}\)
Do \(\sqrt{1}=1;\sqrt{2}+\sqrt{3}+\sqrt{4}< 3.\sqrt{4}=6\)\(;\sqrt{5}+\sqrt{6}+...+\sqrt{9}< 5.\sqrt{9}=15\)
\(\Rightarrow\sqrt{1}+\sqrt{2}+...+\sqrt{9}< 1+6+15=22\)(1)
Cung co:\(5.\sqrt{5}>5.\sqrt{4}=10\)\(\Rightarrow5.\sqrt{5}+12>10+12=22\)(2)
Tu (1) va (2) =>....
a) Có \(\sqrt{2}< \sqrt{2,25}=1,5\)
\(\sqrt{6}< \sqrt{6,25}=2,5\);
\(\sqrt{12}< \sqrt{12,25}=3,5\);
\(\sqrt{20}< \sqrt{20,25}=4,5\)
=> \(P=\sqrt{2}+\sqrt{6}+\sqrt{12}+\sqrt{20}< 1,5+2,5+3,5+4,5=12\)
Vậy P < 12
Answer:
ý a, tham khảo bài làm của @xyzquynhdi
\(\sqrt{2}+\sqrt{3}+\sqrt{5}\)
\(\sqrt{10+\sqrt{24}+\sqrt{40}+\sqrt{60}}\)
\(=\sqrt{10+2\sqrt{6}+2\sqrt{10}+2\sqrt{15}}\)
\(=\sqrt{\left(\sqrt{2}\right)^2+\left(\sqrt{3}\right)^2+\left(\sqrt{5}\right)^2+2\sqrt{2}\sqrt{3}+2\sqrt{2}\sqrt{5}+2\sqrt{3}\sqrt{5}}\)
\(=\sqrt{\left(\sqrt{2}+\sqrt{3}+\sqrt{5}\right)^2}=\sqrt{2}+\sqrt{3}+\sqrt{5}\)
\(3\sqrt{3}=\sqrt{27}\)
Ta có \(27>12\Rightarrow\sqrt{27}>\sqrt{12}\)
\(hay3\sqrt{3}>\sqrt{12}\)
\(\sqrt{12}=3\sqrt{3}>2\sqrt{3}\)
\(\Rightarrow\sqrt{12}< 3\sqrt{3}\)