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Gọi A là biểu thức ta có:
A = 1.2+2.3+3.4+......+99.100
Gấp A lên 3 lần ta có:
A . 3 = 1.2.3 + 2.3.3 + 3.4.3 + … + 99.100.3
A . 3 = 1.2.3 + 2.3.(4 - 1) + 3.4.( 5 - 2) + … + 99.100. (101 - 98)
A . 3 = 1.2.3 + 2.3.4 - 1.2.3 + 3.4.5 - 2.3.4 + … + 99.100.101 - 98.99.100
A . 3 = 99.100.101
A = 99.100.101 : 3
A = 33.100.101
A = 333 300
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2A=1/2+1/6+1/12+1/20+1/30+1/42
=1/1.2+1/2.3+1/3.4+1/4.5+1/5.6+1/6.7
=1/1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7
=1-1/7
=6/7
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\(\frac{15.27^7.3^8-9^{15}}{4^2.81^8}=\frac{3.5.\left(3^3\right)^7.3^8-\left(3^2\right)^{15}}{\left(2^2\right)^2.\left(3^4\right)^8}\)
\(=\frac{3.5.3^{21}.3^8-3^{30}}{2^4.3^{24}}=\frac{3^{32}.5-3^{30}}{2^4.3^{24}}\)
\(=\frac{3^{30}\left(3^2.5-1\right)}{2^4.3^{24}}=\frac{3^6.44}{2^4}=\frac{3^6.2^2.11}{2^4}=\frac{3^6.11}{2^2}\)
Ta có :\(\frac{15.27^7.3^8-9^{15}}{4^2.81^8}=\frac{3.5.\left(3^3\right)^7.3^8-\left(3^2\right)^{15}}{4^2.\left(3^4\right)^8}=\frac{3.5.3^{21}.3^8-3^{30}}{4^2.3^{32}}=\frac{3^{30}.5-3^{30}}{4^2.3^{32}}=\frac{3^{30}.4}{4^2.3^{32}}=\frac{1}{4.3^2}=\frac{1}{36}\)
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a, 15.27 - 3.5.17
= 15.27 - 15. 17
= 15 . ( 27 - 17 )
= 15 . 10
= 150
b, 55 - 5 . ( 20 + 11 )
= 55 - 100 . 55
= 55 . ( 1 - 100 )
= 55 . ( -99 )
= ...
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18.4 + 2.(x-6) = 8.14 + 80
=> 2.[36 + x - 6] = 2.[42 + 40]
30 + x = 82
x = 82 - 30 = 52
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a 15.27-3.5.7=15.27-15.7=15.(27-7)=15.20=300
b 55-5(20+11)=55-5.20+5.11=55-100+55=55.2-100=10
c 37.(29-23)-29.(37-23)=37.29-37.23-29.37-29.23=37.(29-29)-23.(37-29)=0-23.8=0-184=(-184)
tick đúng mình nha làm ơn bạn đó bạn ko tick mình thì bạn sẽ xui cả năm
a, =15.27-15.7
=15.20=300
b,=5.11-5.20-5.11
=5(11-20-11)
=5(-20)=-100
c,=37.29-37.23-29.37+29.23
=37.29-29.37-37.23+29.23
=0+(-37+29).23
=-8.23=-184
a.9 và câu sau là 30 nha
60-26.75-2.35
60-(26.75+3.25)
60-30
30