Viết dạng bình phương một tổng a) 11 + 2√30 b) 10 - 2√21 c) 8 + 2√15 d) 7 + 4√3 e) 9 - 4√2
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b: \(10-2\sqrt{21}=\left(\sqrt{7}-\sqrt{3}\right)^2\)
c: \(8+2\sqrt{15}=\left(\sqrt{5}+\sqrt{3}\right)^2\)
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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/ \(12+6\sqrt{3}=3^2+2.3.\sqrt{3}+\left(\sqrt{3}\right)^2\)
= \(\left(3+\sqrt{3}\right)^2\)
![](https://rs.olm.vn/images/avt/0.png?1311)
b)\(27-10\sqrt{2}=5^2-2.5\sqrt{2}+2=\left(5-\sqrt{2}\right)^2\)
c)\(18-8\sqrt{2}=4^2-2.4\sqrt{2}+2=\left(4-\sqrt{2}\right)^2\)
d)\(4-2\sqrt{3}=3-2\sqrt{3}+1=\left(\sqrt{3}-1\right)^2\)
e)\(6\sqrt{5}+14=9+2.3\sqrt{5}+5=\left(3+\sqrt{5}\right)^2\)
f)\(20\sqrt{5}+45=5^2+2.5.2\sqrt{5}+20=\left(5+2\sqrt{5}\right)^2\)
g)\(7-2\sqrt{6}=6-2\sqrt{6}+1=\left(\sqrt{6}-1\right)^2\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a) 3/2:9/4+21/8
= 3/2 x 4/9 + 21/8
=12/18 + 21/8
= 2/3 + 21/8 = 16/24 + 63/24 = 79/24
b) 3/10+5/2x1/3
=3/10 + 5/6
= 9/30 + 25/30 = 34/30 = 17/15
c) 8/15:3/11+2/15:2/11
= 8/15x11/3 + 2/15x11/2
= 88/45 + 22/30
= 88/45 + 11/15 = 88/45 + 33/45 = 121/45
d) 19/5-11/4:9/8
= 19/5 - 11/4x8/9
= 19/5 - 88/36
= 19/5 - 22/9 = 171/45 - 110/45 = 61/45
e) 33/7:11/6+37/15x21/74
= 33/7x6/11 + 7/10
= 198/77 + 7/10 = 1980/770 + 1386/770 = 153/35
a) 3/2:9/4+21/8
= 3/2 x 4/9 + 21/8
=12/18 + 21/8
= 2/3 + 21/8 = 16/24 + 63/24 = 79/24
b) 3/10+5/2x1/3
=3/10 + 5/6
= 9/30 + 25/30 = 34/30 = 17/15
c) 8/15:3/11+2/15:2/11
= 8/15x11/3 + 2/15x11/2
= 88/45 + 22/30
= 88/45 + 11/15 = 88/45 + 33/45 = 121/45
d) 19/5-11/4:9/8
= 19/5 - 11/4x8/9
= 19/5 - 88/36
= 19/5 - 22/9 = 171/45 - 110/45 = 61/45
e) 33/7:11/6+37/15x21/74
= 33/7x6/11 + 7/10
= 198/77 + 7/10 = 1980/770 + 1386/770 = 153/35
\(a,=\left(\sqrt{6}+\sqrt{5}\right)^2\\ b,=\left(\sqrt{7}-\sqrt{3}\right)^2\\ c,=\left(\sqrt{3}+\sqrt{5}\right)^2\\ d,=\left(2+\sqrt{3}\right)^2\\ e,=\left(2\sqrt{2}-1\right)^2\)
a: \(=\left(\sqrt{6}+\sqrt{5}\right)^2\)
b: \(=\left(\sqrt{7}-\sqrt{3}\right)^2\)