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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/ \(\dfrac{5}{12}.\dfrac{17}{11}-\dfrac{5}{12}.\dfrac{7}{11}+\dfrac{5}{12}.\dfrac{1}{11}\)
\(=\dfrac{5}{12}.\left(\dfrac{17}{11}-\dfrac{7}{11}+\dfrac{1}{11}\right)\)
\(=\dfrac{5}{12}.\left(\dfrac{17-7+1}{11}\right)\)
\(=\dfrac{5}{12}.1\)
\(=\dfrac{5}{12}\)
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!
3/7 *14/5 - 1/2 = 6/5-1/2 = 7/10
2/5 - 3/5 *5/10 = 2/5 - 3/10 = 1/10
4/13 *5/11 + 4/13 *6/11 - 4/13
= 4/13*5/11 +4/13 *6/11 - 4/13 *1
= 4/13 *(5/11+ 6/11 - 1)
= 4/13 *0
=0
a ) \(-\frac{3}{7}.\frac{3}{11}+-\frac{3}{7}.\frac{8}{11}+1\frac{3}{7}\)
\(=-\frac{3}{7}.\left(\frac{3}{11}+\frac{8}{11}\right)+\frac{10}{7}\)
\(=-\frac{3}{7}.\frac{11}{11}+\frac{10}{7}\)
\(=-\frac{3}{7}.1+\frac{10}{7}\)
\(=\frac{10}{7}\)
b ) \(75\%.10,5=\frac{3}{4}.10,5=7,875\)
c ) \(5-3.\left(\left|-4\right|-30:15\right)\)
\(=5-3.\left(4-2\right)\)
\(=5-3.2\)
\(=5-6\)
\(=-1\)
d ) \(-\frac{5}{7}.\frac{2}{11}+-\frac{5}{7}.\frac{9}{11}+1\frac{5}{7}\)
\(=-\frac{5}{7}.\left(\frac{2}{11}+\frac{9}{11}\right)+\frac{12}{7}\)
\(=-\frac{5}{7}.1+\frac{12}{7}\)
\(=\frac{7}{7}\)
\(=1\)
Chúc bạn học tốt !!!