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6/7+(5/8-3/16):5.-4
=6/7+(10/16-3/16):5.-4
=6/7+7/16:5.-4
=6/7+7/80.-4
=6/7+-28/80
=6/7+7/20
120/140+49/140
=169/140
Câu 9
a) 2/15 + (-3/5)
= 2/15 - 3/5
= 2/15 - 9/15
= -7/15
b) -5/7 + 3/7 . (-2/9)
= -5/7 - 2/21
= -15/21 - 2/21
= -17/21
c) 5/16 - (7/15 - 3/16) + 17/30
= 5/16 - 7/15 + 3/16 + 17/30
= (5/16 + 3/16) + (17/30 - 14/30)
= 1/2 + 1/10
= 5/10 + 1/10
= 6/10
= 3/5
\(a,\dfrac{2}{15}+\left(-\dfrac{3}{5}\right)\\ =\dfrac{2}{15}-\dfrac{3}{5}\\ =\dfrac{2}{15}-\dfrac{9}{15}\\ =-\dfrac{7}{15}\\ b,-\dfrac{5}{7}+\dfrac{3}{7}\times\left(-\dfrac{2}{9}\right)\\ =-\dfrac{5}{7}-\dfrac{2}{21}\\ =-\dfrac{15}{21}-\dfrac{2}{21}\\ =-\dfrac{17}{21}\\ c,\dfrac{5}{16}-\left(\dfrac{7}{15}-\dfrac{3}{16}\right)+\dfrac{17}{30}\\ =\dfrac{5}{16}-\dfrac{7}{15}+\dfrac{3}{16}+\dfrac{17}{30}\\ =\left(\dfrac{5}{16}+\dfrac{3}{16}\right)-\left(\dfrac{17}{15}+\dfrac{17}{30}\right)\\ =\dfrac{1}{2}-\dfrac{17}{10}\\ =\dfrac{5}{10}-\dfrac{17}{10}\\ =-\dfrac{6}{5}.\)
16 + (-17) + ........ + 82 + (-83) + 84 = -1 x 34 + 84
= -34 + 84 = 50
=(16-17)+(18-19)+...+(82-83)+84
=-1+(-1)+...+(-1)+84=(-1)*34+84=-34+84=50
43.25.16=(22)3.25.24=26.25.24=215
32.64.82=25.26.26=217
=> A=217:215=217-15=22=4
Đáp số: A=4
\(\frac{32.64.8^2}{4^3\cdot2^5\cdot16}=\frac{2^5.2^6.2^6}{2^6.2^5.2^3}\)
\(=\frac{2^{5+6+6}}{2^{6+5+3}}=\frac{2^{17}}{2^{14}}=2^{17-14}=2^3=8\)
Mình giải thích thêm nha
\(8^2=\left(2^3\right)^2=2^6\)
\(4^3=\left(2^2\right)^3=2^6\)