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Nếu :
1 x 2 x 3 =5
2 x 3 x 4 = 10
3 x 4 x 5 = 17
4 x 5 x 6 = 26
Thì 6 x 7 x 8= 50
k mình nhé ^_^
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\left(1+1+1\right)!=6.\)
\(2+2+2=6\)
\(3.3-3=6\)
\(\sqrt{4}+\sqrt{4}.\sqrt{4}=6\)
\(5+5\div5=6\)
\(6.6\div6=6\)
\(7-7\div7=6\)
\(\sqrt{8+8\div8}!=6\)
\(\sqrt{9}.\sqrt{9}-\sqrt{9}=6\)
\(\sqrt{10-10\div10}!\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Bài 1:
1) Ta có: \(3-2\sqrt{2}\)
\(=2-2\cdot\sqrt{2}\cdot1+1\)
\(=\left(\sqrt{2}-1\right)^2\)
2) Ta có: \(8+2\sqrt{7}\)
\(=7+2\cdot\sqrt{7}\cdot1+1\)
\(=\left(\sqrt{7}+1\right)^2\)
3) Ta có: \(x-2\sqrt{x-1}\)
\(=x-1-2\cdot\sqrt{x-1}\cdot1+1\)
\(=\left(\sqrt{x-1}-1\right)^2\)
4) Ta có: \(6-4\sqrt{2}\)
\(=4-2\cdot2\cdot\sqrt{2}+2\)
\(=\left(2-\sqrt{2}\right)^2\)
5) Ta có: \(7+4\sqrt{3}\)
\(=4+2\cdot2\cdot\sqrt{3}+3\)
\(=\left(2+\sqrt{3}\right)^2\)
6) Ta có: \(9-4\sqrt{5}\)
\(=5-2\cdot\sqrt{5}\cdot2+4\)
\(=\left(\sqrt{5}-2\right)^2\)
7) Ta có: \(10+2\sqrt{21}\)
\(=7+2\cdot\sqrt{7}\cdot\sqrt{3}+3\)
\(=\left(\sqrt{7}+\sqrt{3}\right)^2\)
8) Ta có: \(49+20\sqrt{6}\)
\(=25+2\cdot5\cdot2\sqrt{6}+24\)
\(=\left(5+2\sqrt{6}\right)^2\)
![](https://rs.olm.vn/images/avt/0.png?1311)
(1+1+1)! = 3! = 6
2+2+2=6
3x3-3=6
\(\sqrt{4}+\sqrt{4}+\sqrt{4}=6\)
5:5+5=6
6+(6-6)=6
7-7:7=6
\(8-\sqrt{\sqrt{8+8}}=6\)
\(\sqrt{9}.\sqrt{9}-\sqrt{9}=6\)
![](https://rs.olm.vn/images/avt/0.png?1311)
14dm5cm=14,5dm;3dm7cm=3,7dm
chu vi hình chữ nhật đó là:
(14,5+3,7)x2=36,4(dm)
ĐS:36,4dm
14 dm 5 cm = 14,5 dm
3 dm 7 cm = 3,7 dm
Chiều rộng HCN là :
14,5 - 3,7 = 10,8 ( dm )
chu vi HCN là :
( 14,5 + 10,8 ) x 2 = 50,6 ( dm )
ĐS:..
![](https://rs.olm.vn/images/avt/0.png?1311)
1/ \(7-2\sqrt{6}=\left(\sqrt{6}\right)^2-2\sqrt{6}+1\)
\(=\left(\sqrt{6}-1\right)^2\)
2/ \(10+2\sqrt{21}=\left(\sqrt{7}\right)^2+2.\sqrt{7}.\sqrt{3}+\left(\sqrt{3}\right)^2\)
\(=\left(\sqrt{7}+\sqrt{3}\right)^2\)
4/ \(10+4\sqrt{6}=2^2+2.2.\sqrt{6}+\left(\sqrt{6}\right)^2\)
\(=\left(2+\sqrt{6}\right)^2\)
5/ \(11-2\sqrt{30}=\left(\sqrt{6}\right)^2-2.\sqrt{6}.\sqrt{5}+\left(\sqrt{5}\right)^2\)
= \(\left(\sqrt{6}-\sqrt{5}\right)^2\)
8/ \(11+4\sqrt{7}=2^2+2.2.\sqrt{7}+\left(\sqrt{7}\right)^2\)
= \(\left(2+\sqrt{7}\right)^2\)
10/ \(12+6\sqrt{3}=3^2+2.3.\sqrt{3}+\left(\sqrt{3}\right)^2\)
= \(\left(3+\sqrt{3}\right)^2\)