Tính
3/5+3/7+3/13-3/295 : 4/5+4/7+4/13-4/295
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A=\(\frac{3}{5}\): \(\frac{4}{5}\) + \(\frac{3}{7}\):\(\frac{4}{7}\)+ \(\frac{3}{13}\): \(\frac{4}{13}\)+\(\frac{3}{295}\): \(\frac{4}{295}\)
A= \(\frac{3}{4}\)+ 3/4 + 3/4 + 3/4
A=3/4 . 4 = 3
Ta có: \(\frac{3}{5}+\frac{3}{7}+\frac{3}{13}+\frac{3}{295}=3.\left(1+\frac{1}{5}+\frac{1}{7}+\frac{1}{13}+\frac{1}{295}\right)\)
\(\frac{4}{5}+\frac{4}{7}+\frac{4}{13}+\frac{4}{295}=4.\left(1+\frac{1}{5}+\frac{1}{7}+\frac{1}{13}+\frac{1}{295}\right)\)
\(\Rightarrow\frac{\frac{3}{5}+\frac{3}{7}+\frac{3}{13}+\frac{3}{295}}{\frac{4}{5}+\frac{4}{7}+\frac{4}{13}+\frac{4}{295}}=\frac{3.\left(1+\frac{1}{5}+\frac{1}{7}+\frac{1}{13}+\frac{1}{295}\right)}{4.\left(1+\frac{1}{5}+\frac{1}{7}+\frac{1}{13}+\frac{1}{295}\right)}=\frac{3}{4}\)
\(1,-\dfrac{4}{7}+\dfrac{2}{3}\times\dfrac{-9}{14}\)
\(=\dfrac{-4}{7}+\dfrac{-18}{42}\)
\(=\dfrac{-4\times6}{7\times6}+\dfrac{-18}{42}\)
\(=\dfrac{-20}{42}+\dfrac{-18}{42}\)
\(=-\dfrac{38}{42}\)
\(=-\dfrac{19}{21}\)
\(2,\dfrac{17}{13}-\left(\dfrac{4}{13}-11\right)\)
\(=\dfrac{17}{13}-\dfrac{4}{13}+11\)
\(=\dfrac{13}{13}+11\)
\(=1+11\)
\(=12\)
\(3,8\dfrac{2}{7}-\left(3\dfrac{4}{9}+4\dfrac{2}{7}\right)\)
\(=\dfrac{58}{7}-\left(\dfrac{31}{9}+\dfrac{30}{7}\right)\)
\(=\dfrac{58}{7}-\dfrac{31}{9}-\dfrac{30}{7}\)
\(=\dfrac{58}{7}-\dfrac{30}{7}-\dfrac{31}{9}\)
\(=\dfrac{28}{7}-\dfrac{31}{9}\)
\(=\dfrac{28\times9}{7\times9}-\dfrac{31\times7}{9\times7}\)
\(=\dfrac{252}{63}-\dfrac{217}{63}\)
\(=\dfrac{35}{63}\)
\(=\dfrac{5}{9}\)
\(5,\left(\dfrac{2}{3}-1\dfrac{1}{2}\right):\dfrac{4}{3}+\dfrac{1}{2}\)
\(=\left(\dfrac{2}{3}-\dfrac{3}{2}\right):\dfrac{4}{3}+\dfrac{1}{2}\)
\(=\left(\dfrac{2\times2}{3\times2}-\dfrac{3\times3}{2\times3}\right):\dfrac{4}{3}+\dfrac{1}{2}\)
\(=\left(\dfrac{4}{6}-\dfrac{9}{6}\right):\dfrac{4}{3}+\dfrac{1}{2}\)
\(=\dfrac{-5}{6}:\dfrac{4}{3}+\dfrac{1}{2}\)
\(=\dfrac{-5}{6}\times\dfrac{3}{4}+\dfrac{1}{2}\)
\(=\dfrac{-15}{24}+\dfrac{1}{2}\)
\(=\dfrac{-15}{24}+\dfrac{1\times12}{2\times12}\)
\(=\dfrac{-15}{24}+\dfrac{12}{24}\)
\(=\dfrac{-3}{24}\)
\(=-\dfrac{1}{8}\)
\(6,\dfrac{-5}{13}+\dfrac{2}{5}+\dfrac{-8}{13}+\dfrac{3}{5}-\dfrac{3}{7}\)
\(=\left(\dfrac{-5}{13}+\dfrac{-8}{13}\right)+\left(\dfrac{2}{5}+\dfrac{3}{5}\right)-\dfrac{3}{7}\)
\(=\dfrac{-13}{13}+\dfrac{5}{5}-\dfrac{3}{7}\)
\(=-1+1-\dfrac{3}{7}\)
\(=-\dfrac{3}{7}\)
\(7,\dfrac{6}{5}\times\dfrac{3}{7}+\dfrac{6}{5}:\dfrac{7}{10}+\dfrac{6}{5}\)
\(=\dfrac{6}{5}\times\dfrac{3}{7}+\dfrac{6}{5}\times\dfrac{10}{7}+\dfrac{6}{5}\)
\(=\dfrac{6}{5}\times\left(\dfrac{3}{7}+\dfrac{10}{7}+1\right)\)
\(=\dfrac{6}{5}\times\left(\dfrac{3}{7}+\dfrac{10}{7}+\dfrac{1\times7}{1\times7}\right)\)
\(=\dfrac{6}{5}\times\left(\dfrac{3}{7}+\dfrac{10}{7}+\dfrac{7}{7}\right)\)
\(=\dfrac{6}{5}\times\dfrac{20}{7}\)
\(=\dfrac{120}{35}\)
\(=\dfrac{24}{7}\)
a)-84:4+3^9:3^7+5^0
=-21+(3^9:3^7)+1
=-21+3^2+1
=-21+9+1
=-12+1
=-11
b)295-(31-2^5.5)^2
=295-(31-32.5)^2
=295-(-129)^2
=295+129^2
=295-16641
=-16346
tick cho mk nha bạn
a) -84 : 4 + 3^ 9 : 3 ^ 7 + 5 ^0
=-84:4+3^2+1
=-84:4+9+1
=-21+9+1
=-12+1
=-11
b) 295 - ( 31 - 2^ 5. 5) ^2
= 295 - ( 31 -32. 5)^2
= 295 - (-129)^2
=295-16641
=-16346
\(\frac{6}{5}-\frac{1}{4}+\frac{4}{5}-\frac{3}{4}\)
\(=\left(\frac{6}{5}+\frac{4}{5}\right)-\left(\frac{1}{4}+\frac{3}{4}\right)\)
\(=2-1\)
\(=1\)
\(\frac{7}{9}-\frac{5}{12}+\frac{2}{9}-\frac{7}{12}\)
\(=\left(\frac{7}{9}+\frac{2}{9}\right)-\left(\frac{5}{12}+\frac{7}{12}\right)\)
\(=1-1\)
\(=0\)
các câu sau tương tự
A=1
B=0
C=ÂM 8/15
D=0
E=2
F=3/2
H=2/3
LẦN SAU CHO KHÓ SÍU NHA LỚP 5 CŨNG LÀM ĐC