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= -{100-99+98-97+.....+2-1}
=-{1x50}= -50
tick mình nhà mình đầu tiên
a)
C = 1 − 2 + 3 − 4 + ... + 97 − 98 + 99 − 100 = 1 − 2 + 3 − 4 + ... + 97 − 98 + 99 − 100 = − 1 + − 1 + ... + − 1 + − 1 = − 1.50 = − 50.
b)
B = 1 − 2 − 3 + 4 + 5 − 6 − 7 + ... + 97 − 98 − 99 + 100 = 1 − 2 + − 3 + 4 + 5 − 6 + ... + 97 − 98 + − 99 + 100 = − 1 + 1 + − 1 + ... + − 1 + 1 = − 1 + 1 + − 1 + 1 + ... + − 1 + 1 − 1 = 0 + 0 + ... + 0 − 1 = − 1.
\(A=\frac{-7}{21}+\left(1+\frac{1}{3}\right)\)
\(A=\frac{-7}{21}+1+\frac{1}{3}\)
\(A=\left(\frac{-7}{21}+\frac{1}{3}\right)+1\)
\(A=0+1\\ A=1\)
\(B=\frac{2}{15}+\left(\frac{5}{9}+-\frac{6}{9}\right)\)
\(B=\frac{2}{15}+\frac{-1}{9}\)
\(B=\frac{1}{45}\)
\(C=\left(\frac{-1}{5}+\frac{3}{12}\right)+\frac{-3}{4}\)
\(C=\frac{-1}{5}+\left(\frac{3}{12}+\frac{-3}{4}\right)\)
\(C=\frac{-1}{5}+\frac{-1}{2}\)
\(C=\frac{-7}{10}\)
\(A=\frac{-7}{21}+\left(1+\frac{1}{3}\right)\)
\(A=\frac{-1}{3}+1+\frac{1}{3}\)
\(A=1\)
\(B=\frac{2}{15}+\left(\frac{5}{9}+\frac{-6}{9}\right)\)
\(B=\frac{2}{15}+\frac{5}{9}+\frac{-6}{9}\)
\(B=\frac{2}{15}+\frac{5}{9}+\frac{-10}{15}\)
\(B=\frac{-8}{15}+\frac{5}{9}\)
\(B=\frac{1}{45}\)
\(C=\left(\frac{-1}{5}+\frac{3}{12}\right)+\frac{-3}{4}\)
\(C=\frac{-1}{5}+\frac{3}{4}+\frac{-3}{4}\)
\(C=\frac{-1}{5}\)
a,\(\frac{5}{6}:\frac{-7}{12}\) b, \(\frac{-21}{24}:\frac{-14}{8}\)
d,\(\frac{4}{5}:\frac{-8}{15}\)e,\(\frac{3}{5}+\frac{-7}{4}\)
g,\(\frac{5}{12}-\frac{-7}{12}\)h,\(\frac{-15}{16}.\frac{8}{-25}\)
a) \(2^3.3^2=8.9=72\)
b) \(5^{10}:5^7=5^2=25\)
c) \(2^6:2=2^5=32\)
d) \(7^4:7^4=7^0=1\)
e) \(9^5:9^5=9^0=1\)
c, 12 + 3.24 : 4 - 3
= 12+ 72 :4 -3
= 12+ 18 - 3
= 30 - 3
= 27
d, 5.43 + 2.3 - 81.2
= 215 + 6 - 162
= 221 - 162
= 59
e, 25 : [ 9 - ( 5-3 )2 ] + 6.23
= 25 : [ 9 - 2 . 2 ] + 138
= 25 : [ 9 - 4 ] + 138
= 25 : 5 + 138
= 5 + 138
= 143
a) Cách 1:
\(\begin{array}{l}\left( {\frac{{ - 2}}{{ - 5}} + \frac{{ - 5}}{{ - 6}}} \right) + \frac{4}{5} = \frac{2}{5} + \frac{5}{6} + \frac{4}{5}\\ = \frac{{12}}{{30}} + \frac{{25}}{{30}} + \frac{{24}}{{30}} = \frac{{61}}{{30}}\end{array}\)
Cách 2:
\(\begin{array}{l}\left( {\frac{{ - 2}}{{ - 5}} + \frac{{ - 5}}{{ - 6}}} \right) + \frac{4}{5} = \left( {\frac{2}{5} + \frac{4}{5}} \right) + \frac{5}{6}\\ = \frac{6}{5} + \frac{5}{6} = \frac{{36}}{{30}} + \frac{{25}}{{30}} = \frac{{61}}{{30}}\end{array}\)
b) Cách 1:
\(\begin{array}{l}\frac{{ - 3}}{{ - 4}} + \left( {\frac{{11}}{{ - 15}} + \frac{{ - 1}}{2}} \right) = \frac{3}{4} + \frac{{ - 11}}{{15}} + \frac{{ - 1}}{2}\\ = \frac{{45}}{{60}} + \frac{{ - 44}}{{60}} + \frac{{ - 30}}{{60}}\\ = \frac{{ - 29}}{{60}}\end{array}\).
Cách 2:
\(\begin{array}{l}\frac{{ - 3}}{{ - 4}} + \left( {\frac{{11}}{{ - 15}} + \frac{{ - 1}}{2}} \right) = \frac{3}{4} + \frac{{ - 11}}{{15}} + \frac{{ - 1}}{2}\\ = \left( {\frac{3}{4} + \frac{{ - 1}}{2}} \right) + \frac{{ - 11}}{{15}}\\ = \left( {\frac{3}{4} + \frac{{ - 2}}{4}} \right) + \frac{{ - 11}}{{15}}\\ = \frac{1}{4} + \frac{{ - 11}}{{15}}\\ = \frac{{15}}{{60}} + \frac{{ - 44}}{{60}}\\ = \frac{{ - 29}}{{60}}\end{array}\)