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1 phần 2 nhân 3 phần 4 cộng 1 phần 2 nhân 1 phần 4 ; 11 phần 3 nhân 26 phần 7 trừ 20 phần 7 nhân 8 phần 30
kí hiệu /:phần,kí hiệu'."nhân
a)5/4-5/8+-2/3=30/24+15/24+(-16/24)=29/24
b)7/19.8/11+7/19.3/11+12/19
=7/19.(8/11+3/11)+12/19
=7/19.11/11+12/19
=7/19.1+12/19
=7/19+2/19=9/19
chúc học tốt!
Bài 1: Tính
1/ \(\dfrac{-2}{-5}-\left(\dfrac{-4}{3}\right)\)
\(=\dfrac{2}{5}-\left(\dfrac{-4}{3}\right)\)
\(=\dfrac{6}{15}-\left(\dfrac{-20}{15}\right)\)
\(=\dfrac{6-\left(-20\right)}{15}\)
\(=\dfrac{26}{15}\)
2/ \(\left(\dfrac{-2}{4}-\dfrac{1}{2}\right):\dfrac{2}{3}\)
\(=\left(\dfrac{-2}{4}-\dfrac{2}{4}\right):\dfrac{2}{3}\)
\(=-1:\dfrac{2}{3}\)
\(=-1.\dfrac{3}{2}\)
\(=\dfrac{-3}{2}\)
3/ \(\dfrac{5}{12}.\dfrac{17}{11}-\dfrac{5}{12}.\dfrac{7}{11}+\dfrac{5}{12}.\dfrac{1}{11}\)
\(=\dfrac{5}{12}.\left(\dfrac{17}{11}-\dfrac{7}{11}+\dfrac{1}{11}\right)\)
\(=\dfrac{5}{12}.\left(\dfrac{17-7+1}{11}\right)\)
\(=\dfrac{5}{12}.1\)
\(=\dfrac{5}{12}\)
\(\frac{5^{11}.7^{12}+5^{11}.7^{11}}{5^{12}.7^{11}+9.5^{11}.7^{11}}\)
\(=\frac{5^{11}.7^{11}.7^1+5^{11}.7^{11}}{5^{11}.5^1.7^{11}+3^2.5^{11}.7^{11}}\)
\(=\frac{5^{11}.\left(7^{11}+7^{11}\right).7^1}{5^{11}.\left(7^{11}+7^{11}\right).5^1.3^2}\)
\(=\frac{7}{5.3^2}\)
\(=\frac{7}{45}\)
\(\dfrac{-5}{12}.\dfrac{2}{11}+\dfrac{-5}{12}.\dfrac{9}{11}+\dfrac{5}{12}\)
\(=\dfrac{-5}{12}\left(\dfrac{2}{11}+\dfrac{9}{11}-1\right)\)
\(=\dfrac{-5}{12}\left(1-1\right)\)
\(=0\)