Bài 1 :Tính nhanh
A=2/7+-3/8+11/7+1/3+1/7+5/-8
B=-3/8+12/25+5/-8+2/-5+13/25
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DD
0
DD
1
10 tháng 1 2018
A=2/7+-3/8+11/7+1/3+1/7+5/-8
A=(2/7 + 1/7 + 11/7) + (-3/8 + 5/-8) + 1/3
A=2 + (-1) + 1/3
A=1 + 1/3
A=4/3
B=-3/8+12/25+5/-8+2/-5+13/25
B=(-3/8 + 5/-8) + (12/25 + 13/25) + 2/-5
B=-1 + 1 + 2/-5
B=-2/5
19 tháng 2 2017
\(A=\frac{2}{7}+\left(-\frac{3}{8}\right)+\frac{11}{7}+\frac{1}{3}+\frac{1}{7}+\left(-\frac{5}{8}\right)\)
\(=\left(\frac{2}{7}+\frac{11}{7}+\frac{1}{7}\right)+\left(-\frac{3}{8}-\frac{5}{8}\right)+\frac{1}{3}\)
\(=2-1+\frac{1}{3}\)
\(=1+\frac{1}{3}\)
\(=\frac{4}{3}\)
\(B=-\frac{3}{17}+\left(\frac{2}{3}+\frac{3}{17}\right)\)
\(=-\frac{3}{17}+\frac{2}{3}+\frac{3}{17}\)
\(=\left(-\frac{3}{17}+\frac{3}{17}\right)+\frac{2}{3}\)
\(=0+\frac{2}{3}\)
\(=\frac{2}{3}\)
19 tháng 2 2017
\(C=\frac{3}{8}+\frac{12}{25}+\frac{5}{-8}+\frac{2}{-5}+\frac{13}{25}\)
\(=\left(\frac{3}{8}-\frac{5}{8}\right)+\left(\frac{12}{25}+\frac{13}{25}\right)-\frac{2}{5}\)
\(=-\frac{1}{4}+1-\frac{2}{3}\)
\(=\frac{1}{12}\)
LT
1
14 tháng 6 2022
\(A=\left(\dfrac{2}{7}+\dfrac{11}{7}+\dfrac{1}{7}\right)+\left(\dfrac{-3}{8}+\dfrac{-5}{8}\right)+\dfrac{1}{3}=2-1+\dfrac{1}{3}=1+\dfrac{1}{3}=\dfrac{4}{3}\)
\(B=\dfrac{-3}{8}+\dfrac{12}{25}+\dfrac{-5}{8}+\dfrac{-2}{5}+\dfrac{13}{25}=1+1-\dfrac{5}{8}=-\dfrac{5}{8}\)
7 tháng 4 2021
a) Ta có: \(A=\dfrac{2}{7}+\dfrac{-3}{8}+\dfrac{11}{7}+\dfrac{1}{3}+\dfrac{1}{7}+\dfrac{5}{-8}\)
\(=\left(\dfrac{2}{7}+\dfrac{11}{7}+\dfrac{1}{7}\right)+\left(\dfrac{-3}{8}+\dfrac{-5}{8}\right)+\dfrac{1}{3}\)
\(=2-1+\dfrac{1}{3}\)
\(=1+\dfrac{1}{3}=\dfrac{4}{3}\)
b) Ta có: \(B=\dfrac{-3}{8}+\dfrac{12}{25}+\dfrac{5}{-8}+\dfrac{2}{-5}+\dfrac{13}{25}\)
\(=\left(\dfrac{-3}{8}+\dfrac{-5}{8}\right)+\left(\dfrac{12}{25}+\dfrac{13}{25}\right)+\dfrac{-2}{5}\)
\(=-1+1+\dfrac{-2}{5}\)
\(=-\dfrac{2}{5}\)
7 tháng 4 2021
Giải:
A= 2/7+ -3/8 +11/7 +1/3 + 1/7 + 5/-8
A= (2/7+11/7+1/7)+(-3/8+-5/8)+1/3
A= 2+ (-1) + 1/3
A= 1+1/3
A= 4/3
B= -3/8 + 12/25 + 5/-8 + 2/-5 + 13/25
B= (-3/8+-5/8) + (12/25+13/25) + -2/5
B= -1 + 1 + -2/5
B=-2/5
Chúc bạn học tốt!
31 tháng 3 2023
1: =72/90+65/90=137/90
2: =24/56-77/56=-53/56
3: =-7/10+4/5=1/10
4: =15/100-4/100=11/100
5: =4/6-5/6=-1/6
6: =10/40-15/40-76/40=-81/40
31 tháng 3 2023
7: =-9/10+7/18
=-81/90+35/90=-46/90=-23/45
8: =27/90-55/90=-28/90=-14/45
9: =36/60-50/60-35/60=-49/60
10: =-4/9+5/6-3/8
=-32/72+60/72-27/72
=1/72
14 tháng 3 2018
a, A= 1/5.6+1/6.7+1/7.8+...+1/24.25
=1/5-1/6+1/6-1/7+1/7-1/8+...+1/24-1/25
=1/5-1/25
=4/25
hok tốt k nha
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+(-1)+1/3 =1+1/3 =4/3
B=-3/8+12/25+5/-8+2/-5+13/25
=(-3/8-5/8)+(12/25+13/25)-5/8
=-1+1-5/8= -5/8