Phương pháp giải:

Tính nhẩm các số rồi điền kết quả vào chỗ trống.

Lời giải chi tiết:

Tính nhẩm:

|(5/8-5/14)+(3/8-9/14)|:4/7

=|(5/8+3/8)+(-5/14-9/14)|:4/7

=|1+(-1)|:4/7

=0

`A = ( 5 / 8 - 5 / 14 ) : 4 / 7 + ( 3 / 8 - 9 / 14 ) : 4 / 7`

`A = ( 5 / 8 - 5 / 14 + 3 / 8 - 9 / 14 ) : 4 / 7`

`A = [ ( 5 / 8 + 3 / 8 ) - ( 5 / 14 + 9 / 14 ) ] . 7 / 4`

`A = ( 8 / 8 - 14 / 14 ) . 7 / 4`

`A = ( 1 - 1 ) . 7 / 4 = 0 . 7 / 4 = 0`

\(A=\left(\dfrac{5}{8}-\dfrac{5}{14}\right)\times\dfrac{7}{4}+\left(\dfrac{3}{8}-\dfrac{9}{14}\right)\times\dfrac{7}{4}\)

\(A=\left(\dfrac{5}{8}-\dfrac{5}{14}+\dfrac{3}{8}-\dfrac{9}{14}\right)\times\dfrac{7}{4}\)

\(A=\left(1-1\right)\times\dfrac{7}{4}=0\)

Phương pháp giải:

Tính nhẩm từ trái sang phải rồi điền kết quả vào chỗ trống. 

Lời giải chi tiết:

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a, \(\frac{-3}{7}+\frac{5}{13}-\frac{4}{7}+\frac{8}{13}\)

\(=\frac{-3}{7}-\frac{4}{7}+\frac{5}{13}+\frac{8}{13}\)

\(=-\frac{7}{7}+\frac{13}{13}=-1+1=0\)

b, \(\frac{-5}{14}-\frac{2}{-14}+\frac{1}{8}+\frac{1}{8}\)

\(=\frac{-5}{14}+\frac{2}{14}+\frac{1}{8}+\frac{1}{8}\)

\(=-\frac{3}{14}+\frac{1}{4}=\frac{1}{28}\)

c,\(-\frac{5}{13}-\left(\frac{3}{5}+\frac{3}{13}-\frac{4}{10}\right)\)

\(=-\frac{5}{13}-\frac{3}{13}-\frac{3}{5}+\frac{4}{10}\)

\(=-\frac{8}{13}-\frac{3}{5}+\frac{4}{10}=-\frac{79}{65}+\frac{4}{10}=-\frac{53}{65}\)

d, \(\left[\left(\frac{1}{8}-\frac{9}{7}+\frac{4}{6}-\frac{12}{7}-\frac{1}{2}\right)+\frac{5}{9}\right]\)

\(=\left[\left(\frac{1}{8}-\frac{9}{7}+\frac{2}{3}-\frac{12}{7}-\frac{1}{2}\right)+\frac{5}{9}\right]\)

\(=\left[\left(\frac{1}{8}-\frac{1}{2}-\frac{9}{7}-\frac{12}{7}+\frac{2}{3}\right)+\frac{5}{9}\right]\)

\(=-\frac{65}{24}+\frac{5}{9}=-2\frac{11}{72}\)

a)-3/7+5/13-4/7+8/13

=-3/7-4/7+5/13+8/13

=-7/7+13/13

=-1+1

=0

a: =35/17-18/17-9/5+4/5

=1-1=0

b: =-7/19(3/17+8/11-1)

=7/19*18/187=126/3553

c: =26/15-11/15-17/3-6/13

=1-6/13-17/3

=7/13-17/3=-200/39

a.

                     N= 30

b. \(X=\dfrac{5.4+7.3+8.8+9.8+10.4+14.3}{30}\approx8,6\left(phút\right)\)

Mốt của dấu hiệu là 9

a,

b, 
X=\(\dfrac{5.4+7.3+8.8+9.8+10.4+14.3}{30}\)
X=\(\dfrac{259}{30}\)
Mo=8;9

Số điểm(x):5,4,9,6,10,7,8

Tần số(n):3,2,6,7,2,5,5(N=30)

Số trung bình cộng là: Nhân số điểm với tần số:30=107/15~~7,1

a: \(=\dfrac{5}{14}\left(\dfrac{2}{9}+\dfrac{7}{9}+1\right)=\dfrac{5}{14}\cdot2=\dfrac{5}{7}\)

b: \(=\dfrac{6}{8}\left(\dfrac{6}{7}-6\right)=\dfrac{6}{8}\cdot\dfrac{-36}{7}=\dfrac{-216}{56}=\dfrac{-27}{7}\)