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\(a,\dfrac{2}{3}-\dfrac{5}{6}+\dfrac{3}{4}\)
\(=(\dfrac{2}{3}+\dfrac{3}{4})-\dfrac{5}{6}\)
\(=\dfrac{7}{12}\)
\(b,\dfrac{6}{7}.\dfrac{8}{13}+\dfrac{6}{13}.\dfrac{9}{7}-\dfrac{-4}{13}.\dfrac{6}{7}\)
\(=\dfrac{6}{7}.(\dfrac{8}{13}-\dfrac{4}{13})+(\dfrac{6}{13}.\dfrac{9}{7})\)
\(=(\dfrac{6}{7}.\dfrac{4}{13})+\dfrac{54}{91}\)
\(=\dfrac{24}{91}+\dfrac{54}{91}\)
\(=\dfrac{78}{91}=\dfrac{6}{7}\)
\(c,19.(-26)\)
\(=-494\)
a) `2/3 - 5/6 +3/4`
`=4/6-5/6+3/4`
`=-1/6+3/4`
`=-4/24+18/24`
`=14/24=7/12`
b) `6/7 .8/13 +6/13 .9/7 -4/13 .6/7`
`=6/7 .(8/13-4/13) + 6/13 .9/7`
`=6/7 . 4/13 + 6/13 . 9/7`
`= 6/13 .4/7 +6/13 .9/7`
`=6/13 . (4/7+9/7)`
`=6/13 . 13/7`
`=6/7`
c) `19.(-26)`
`=(1-20).(20+6)`
`=20+6-400-120`
`=-494`

Câu 1 dễ mà :
1.2.3...9 - 1.2.3...8 - 1.2.3...7.82
= 1.2.3...8.9 - 1.2.3...8.1 - 1.2.3...7.8.8
= 1.2.3...8.( 9 - 1 - 8 )
= 1.2.3...8.0
= 0

- 6/7.8/13+6/13.9/7-3/13.6/7
- (-3,2).15/64+(0,8-2 4/15):3 2/3
- 1,4.15/49-(4/5+2/3):2 1/5
/ là phân số
1.=6/7.8/13+6/7.9/13-3/13.6/7=6/7.(8/13+9/13-3/13)=6/7.14/13=12/13

a) =\(\left[\left(12+1\right)^2+\left(12+2\right)^2\right]:\left(13^2+14^2\right)\)
=1
b)=(1.2.3....8).(9-1-8)
=(1.2.3....8).0
=0
mik chỉ giải được zậy thôi.
t mik nha.

A = \(\dfrac{1}{4}.\dfrac{7}{3}.12\)
= \(\dfrac{1.7.12}{4.3}\)
= \(7\)
@Nguyễn Thành Đăng
B = \(\dfrac{3}{8}.56.\dfrac{25}{7}.\left(-4\right)\)
= \(-\dfrac{3.56.25.4}{8.7}\)
= -3.100
= -300
@Nguyễn Thành Đăng

a)\(\frac{2}{3}+\frac{3}{4}+\frac{5}{6}\)
\(=\frac{8+9+10}{12}\)
\(=\frac{27}{12}=\frac{9}{4}\)
b)\(\frac{15}{8}-\frac{7}{12}+\frac{5}{6}\)
\(=\frac{45-14+20}{24}\)
\(=\frac{51}{24}=\frac{17}{8}\)
2)
a)\(\frac{2}{5}+\frac{7}{13}+\frac{3}{5}+\frac{1}{7}\)
\(=\frac{2}{5}+\frac{3}{5}+\frac{7}{13}+\frac{1}{7}\)
\(=1+\frac{7}{13}+\frac{1}{7}\)
\(=\frac{20}{13}+\frac{1}{7}\)
\(=\frac{153}{91}\)
Tí tớ trả lời tiếp
b)\(5\frac14+3\frac25-4\frac14\)
=\(\left(5\frac14-4\frac14\right)+3\frac25\)
=\(\left\lbrack\left(5-4\right)+\left(\frac14-\frac14\right)\right\rbrack+\frac{17}{5}\)
=\(1+0+\frac{17}{5}\)
=\(\frac55+\frac{17}{5}\)
=\(\frac{22}{5}\)

\(a,13\frac{3}{7}+4\frac{5}{13}-8\frac{3}{7}\)
\(=\left(13+4-8\right)+\left(\frac{3}{7}+\frac{5}{13}-\frac{3}{7}\right)\)
\(=9\frac{5}{13}\)
\(b,\left(6-2\frac{4}{5}\right).3\frac{1}{8}-1\frac{3}{5}:\frac{1}{4}\)
\(=3\frac{1}{5}.3\frac{1}{8}-1\frac{3}{5}.4\)
\(=10-6\frac{2}{5}\)
\(=3\frac{3}{5}\)

a) A = 3/7
b) B = 73/13
c) C = 37/7
d) D = 12
ba câu a) ,b) ,c) bn đổi ra hỗn số giúp mk nha
tick cho tớ nha

A = 6/19 . -7/11 + 6/19 . -4/11 + -13/19
A = 6/19 . [-7/11 + (-4/11)] + (-13/19)
A = 6/19 . -11/11 + (-13/19)
A = 6/19 . (-1) + (-13/19)
A = -6/19 + (-13/19)
A = -19/19
A = -1
Vậy A = -1
A=1
B=6/7
\(A=-\dfrac{3}{4}+\left[2+\left(-\dfrac{1}{4}\right)\right]\\ =-\dfrac{3}{4}+2-\dfrac{1}{4}\\ =-\left(\dfrac{3}{4}+\dfrac{1}{4}\right)+2\\ =\left(-1\right)+2=1\\ B=\dfrac{6}{7}\cdot\dfrac{8}{13}+\dfrac{6}{7}\cdot\dfrac{9}{13}-\dfrac{4}{13}\cdot\dfrac{6}{7}\\ =\dfrac{6}{7}\cdot\left(\dfrac{8}{13}+\dfrac{9}{13}-\dfrac{4}{13}\right)\\ =\dfrac{6}{7}\cdot\dfrac{13}{13}=\dfrac{6}{7}\)