\(\frac{9}{4}.\frac{7}{17}+2\frac{1}{4}.\frac{3}{17}-2,25.\frac{13}{17}\)

\(=\frac{9}{4}.\frac{7}{17}+\frac{9}{4}.\frac{3}{17}-\frac{9}{4}.\frac{13}{17}\)

\(=\frac{9}{4}.\left(\frac{7}{17}+\frac{3}{17}-\frac{13}{17}\right)\)

\(=\frac{9}{4}.\frac{-3}{17}\)

\(=\frac{-27}{68}\)

Nhớ k cho mình nhé 

684 phút 42 giây

=6,75 giờ +11,2 giờ + 16,8 giờ - 9,8 giờ

=24,95 giờ

75

k mk nha

mk k lại cho!

3 + 4 + 5 + 5 + 6 + 7 + 8 + 10 + 10 + 3 + 4 + 5 + 5 + 6 + 7

= (3 + 7) + (3 + 7) + (4 + 6) + (4 + 6) + (5 + 5) + (5 + 5) + 10 + 10

=     10   +    10    +    10    +     10   +     10   +    10    + 10 + 10

=     80

=(3+7)+(4+6)+(5+5)+(3+7)+(4+6)+(5+5)+10+10

=10+10+10+10+10+10+10+10

=80

\(50\%.\frac{4}{3}.10.\frac{7}{35}.0,75\)

\(=\frac{1}{2}.\frac{4}{3}.10.\frac{7}{35}.\frac{3}{4}\)

\(=\left(\frac{1}{2}.10\right)\times\left(\frac{4}{3}.\frac{3}{4}\right).\frac{7}{35}\)

\(=5.1.\frac{7}{35}\)

\(=\frac{35}{35}=1\)

~ Hok tốt ~

\(\frac{3}{1.4}+\frac{3}{4.7}+\frac{3}{7.10}+...+\frac{3}{40.43}\)

\(=1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+...+\frac{1}{40}-\frac{1}{43}\)

\(=1+\left(\frac{1}{4}-\frac{1}{4}\right)+\left(\frac{1}{7}-\frac{1}{7}\right)+...+\left(\frac{1}{40}-\frac{1}{40}\right)-\frac{1}{43}\)

\(=1-\frac{1}{43}=\frac{42}{43}\)

~ Hok tốt ~

câu a) có trong đề cương của tui 

Mình sửa đề 1 chút

\(\frac{3}{1\cdot4}+\frac{3}{4\cdot7}+\frac{3}{7\cdot10}+....+\frac{3}{19\cdot22}\)

\(=1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+....+\frac{1}{19}-\frac{1}{22}\)

\(=1-\frac{1}{22}=\frac{20}{22}=\frac{10}{11}\)

3/1x4+3/4x7+3/7x10+...+3/19x22

=3/1-3/4+3/4-3/7+3/7-3/10+...+3/19-3/22

=1-1/4+1/4-1/7+1/7-1/10+...+1/19-1/22

=(1/4-1/4)+(1/7-1/7)+(1/10-1/10)+...+(1/19-1/19)+(1-1/22)

=0+0+0+...+0+21/22

=21/22

\(B=\left(8-2,25+\dfrac{2}{7}\right)-\left(-6-\dfrac{3}{7}+1\dfrac{1}{4}\right)-\left(3+0,5-1\dfrac{2}{7}\right)\\ B=8-\dfrac{9}{4}+\dfrac{2}{7}+6+\dfrac{3}{7}-\dfrac{5}{4}-3-\dfrac{1}{2}+\dfrac{9}{7}\\ B=\left(8+6-3\right)+\left(-\dfrac{9}{4}-\dfrac{5}{4}\right)+\left(\dfrac{2}{7}+\dfrac{3}{7}+\dfrac{9}{7}\right)-\dfrac{1}{2}\)

\(B=11-\dfrac{7}{2}+2-\dfrac{1}{2}\\ B=\left(11+2\right)+\left(-\dfrac{7}{2}-\dfrac{1}{2}\right)\\ B=13-4\\ B=9.\)

\(A=\frac{3^2}{1.4}+\frac{3^2}{4.7}+\frac{3^2}{7.10}+...+\frac{3^2}{97.100}\)

\(A=\frac{3^2}{3}\cdot\left(1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+....+\frac{1}{97}-\frac{1}{100}\right)\)

\(A=3\cdot\left(1-\frac{1}{100}\right)\)

\(A=3\cdot\frac{99}{100}=\frac{297}{100}\)

Vậy \(A=\frac{297}{100}\)