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Cách 1: A = 1/2 x 2/3 - 1/2 x 2/3
A = 0
Cách 2: A = 1/2 : 3/2 - 1/2 : 3/2
A = 0
a: Thay a=9 và b=15 vào P, ta được:
\(P=\left(9+1\right)\cdot2+\left(15+1\right)\cdot3\)
\(=10\cdot2+16\cdot3=20+48=68\)
b: \(m=2\cdot a+3\cdot b+5=2\cdot9+3\cdot15+5=68\)
mà P=68
nên P=m
(2/5 + 1/2 + 3/10) : 3
= (4/10 + 5/10 + 3/10) : 3
= 6/5 . 1/3
= 6/15
\(\frac{9}{2}-\frac{8}{3}:\frac{2}{3}+\frac{1}{2}=\frac{9}{2}-4+\frac{1}{2}=\frac{1}{2}+\frac{1}{2}=1\)
\(\frac{12}{5}:\frac{4}{7}-\frac{1}{2}=\frac{21}{5}-\frac{1}{2}=\frac{37}{10}\)
A) 9/2 - 8/3 : 2/3 + 1/2 = 9/2 - 8/3 x 3/2 + 1/2
= 9/2 - 4 + 1/2
= 1/2 + 1/2
= 1.
B) 12/5 : 4/7 - 1/2 = 12/5 x 7/4 - 1/2
= 21/5 -1/2
= 21/10.
\(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+....+\frac{1}{98.99}+\frac{1}{99.100}\)
\(=\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{98}-\frac{1}{99}+\frac{1}{99}-\frac{1}{100}\)
\(=\frac{1}{1}-\frac{1}{100}=\frac{99}{100}\)
ĐẶT : A= \(\frac{1}{1.2}+\frac{1}{2.3}+...+\frac{1}{98.99}\)\(\)
= \(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{98}-\frac{1}{99}\)
= \(1-\frac{1}{99}=\frac{98}{99}\)
\(\dfrac{11}{2}\): \(\dfrac{1}{4}\) \(\times\) \(\dfrac{5}{3}\)
= \(\dfrac{11}{2}\) \(\times\) \(\dfrac{4}{1}\) \(\times\) \(\dfrac{5}{3}\)
= 22 \(\times\) \(\dfrac{5}{3}\)
= \(\dfrac{110}{3}\)
\(\dfrac{5}{2}-\dfrac{1}{4}+\dfrac{5}{3}\)
= \(\dfrac{30}{12}-\dfrac{3}{12}+\dfrac{20}{12}\)
= \(\dfrac{7}{12}\)
\(\dfrac{14}{5}\times\dfrac{2}{3}\)+ 5
= \(\dfrac{28}{15}\) + 5
= \(\dfrac{28}{15}\) + \(\dfrac{75}{15}\)
= \(\dfrac{103}{15}\)
\(\frac{2}{3}+\frac{3}{4}:\frac{6}{7}+\frac{1}{8}\cdot\frac{4}{3}\)
\(=\frac{2}{3}+\frac{3}{4}\cdot\frac{7}{6}+\frac{1}{8}\cdot\frac{4}{3}\)
\(=\frac{2}{3}+\frac{21}{24}+\frac{4}{24}\)
\(=\frac{16}{24}+\frac{21}{24}+\frac{4}{24}\)
\(=\frac{37}{24}+\frac{4}{24}\)
\(=\frac{41}{24}\)
2/3 + 3/4 : 6/7 + 1/8 x 4/3 = 2/3 + 7/8 + 1/6
= 16/24 + 21/24 + 4/24
= 41/24
= 3/4 + 5/6 x 3/2 + 1/5
= 3/4 + 5/4 + 1/5
= 15/20 + 25/20 + 4/20
= 44/20
= 11/5
TL
\(\frac{3}{4}+\frac{5}{6}:\frac{2}{3}+\frac{1}{5}\)
\(=\frac{3}{4}+\frac{5}{4}+\frac{1}{5}\)
\(=\frac{11}{5}\)
nhaaaaaaa
HT
\(\frac{2}{3}+\frac{1}{2}:3\)
\(=\frac{2}{3}+\frac{1}{2.3}\)
\(=\frac{4}{6}+\frac{1}{6}\)
\(=\frac{5}{6}\)
\(\frac{2}{3}+\frac{1}{2}:3\)
\(=\frac{2}{3}+\frac{1}{6}\)
\(=\frac{5}{6}\)