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23 tháng 2 2021

mik ko hieu lam

9 tháng 4 2018

a) 2/7+-3/8+11/7+1/3+1/7+5/-8

=(2/7+11/7+1/7)+(3/8+-5/8)+1/3

=2+2+1/3

=4+1/3

=13/3

b) -3/8+12/25+5/-8+2/-5+13/25

=(-3/8+-5/8)+(12/25+13/25)+-2/5

=-1+1+-2/5

=0+-2/5

=-2/5

c)7/8+1/8*3/8+1/8*5/8

=7/8+1/8*(3/8+5/8)

=7/8+1/8*1

=7/8+1/8

=1

9 tháng 4 2018

a) 2/7+-3/8+11/7+1/3+1/7+5/-8

=(2/7+11/7+1/7)+(3/8+-5/8)+1/3

=2+2+1/3

=4+1/3

=13/3

b) -3/8+12/25+5/-8+2/-5+13/25

=(-3/8+-5/8)+(12/25+13/25)+-2/5

=-1+1+-2/5

=0+-2/5

=-2/5

c)7/8+1/8*3/8+1/8*5/8

=7/8+1/8*(3/8+5/8)

=7/8+1/8*1

=7/8+1/8

=1

15 tháng 3 2018

\(a)\) \(A=\frac{5\left(2^2.3^2\right)^9.\left(2^2\right)^6-2\left(2^2.3\right)^{14}.3^4}{5.2^{28}.3^{18}-7.2^{29}.3^{18}}\)

\(A=\frac{2^{30}.3^{18}.5-2^{29}.3^{18}}{2^{28}.3^{18}.5-2^{29}.3^{18}.7}\)

\(A=\frac{2^{29}.3^{18}\left(2.5-1\right)}{2^{28}.3^{18}\left(5-2.7\right)}\)

\(A=\frac{2\left(10-1\right)}{5-14}\)

\(A=\frac{2.9}{-9}\)

\(A=-2\)

Vậy \(A=-2\)

\(b)\) \(B=81.\left[\frac{12-\frac{12}{7}-\frac{12}{289}-\frac{12}{85}}{4-\frac{4}{7}-\frac{4}{289}-\frac{4}{85}}:\frac{5+\frac{5}{13}+\frac{5}{169}+\frac{5}{91}}{6+\frac{6}{13}+\frac{6}{169}+\frac{6}{91}}\right].\frac{158158158}{711711711}\)

\(B=81.\left[\frac{12\left(1-\frac{1}{7}-\frac{1}{289}-\frac{1}{85}\right)}{4\left(1-\frac{1}{7}-\frac{1}{289}-\frac{1}{85}\right)}:\frac{5\left(1+\frac{1}{13}+\frac{1}{169}+\frac{1}{91}\right)}{6\left(1+\frac{1}{13}+\frac{1}{169}+\frac{1}{91}\right)}\right].\frac{158158158}{711711711}\)

\(B=81.\left[\frac{12}{4}:\frac{5}{6}\right].\frac{2}{9}\)

\(B=81.\frac{18}{5}.\frac{2}{9}\)

\(B=\frac{324}{5}\)

Vậy \(B=\frac{324}{5}\)

Chúc bạn học tốt ~ ( mỏi tay qué >_< )