2/3+4/5=10/15+12/15=22/15

4/6+8/12=8/12+8/12=16/12=4/3

99/17+100/17=199/17

67/12-7/6=67/12-14/12=53/12

65/18-8/6=65/18-24/18=41/18

\(\frac{2}{3}+\frac{4}{5}=\frac{22}{15}\)

\(\frac{4}{6}+\frac{8}{12}=\frac{4}{3}\)

\(\frac{99}{17}+\frac{100}{17}=\frac{199}{17}\)

\(\frac{67}{12}-\frac{7}{6}=\frac{53}{12}\)

`a,`

`31/23-(7/32+8/23)`

`=31/23-7/32-8/23`

`=(31/23-8/23)-7/32`

`=1-7/32=25/32`

`b,`

`38/45-(8/45-17/51-3/11)`

`=38/45-8/45+17/51+3/11`

`= (38/45-8/45)+17/51+3/11`

`=2/3+17/51+3/11`

`=1+3/11=14/11`

`c,`

`(1/3+12/67+13/41)-(79/67-28/41)`

`= 1/3+12/67+13/41-79/67+28/41`

`= 1/3+(12/67-79/67)+(13/41+28/41)`

`= 1/3+(-1)+1=1/3+(-1+1)=1/3+0=1/3`

`d,`

`1/5+(-1/6)+1/7+(-1/8)+1/9+1/8+(-1/7)+1/6+(-1/5)`

`= (1/5+ -1/5)+(-1/6+1/6)+(1/7+ -1/7)+(-1/8 +1/8)+1/9`

`= 0+0+0+0+1/9=1/9 .`

a,(-67.77) - (-67.44) - 77.44+77.67

= (-67).(77-44)-77.(44+67)

= (-67-77).(77-44+44+67)

=-144.144

=-20736

b,[-36:(-12)]-12.8+6³-1

=3-12.8+216-1

=3-96+216-1

=122

=???

ok chị

cái nịt

= 83,00000108

149

149

149

\(\dfrac{11}{8}:x-\dfrac{2}{5}+-\dfrac{1}{6}=-\dfrac{1}{5}\\ =>\dfrac{11}{8}:x-\dfrac{2}{5}=-\dfrac{1}{5}-\left(-\dfrac{1}{6}\right)\\ =>\dfrac{11}{8}:x-\dfrac{2}{5}=-\dfrac{1}{5}+\dfrac{1}{6}\\ =>\dfrac{11}{8}:x-\dfrac{2}{5}=-\dfrac{6}{30}+\dfrac{5}{30}\\ =>\dfrac{11}{8}:x-\dfrac{2}{5}=-\dfrac{1}{30}\\ =>\dfrac{11}{8}:x=-\dfrac{1}{30}+\dfrac{2}{5}\\ =>\dfrac{11}{8}:x=-\dfrac{1}{30}+\dfrac{12}{30}\\ =>\dfrac{11}{8}:x=\dfrac{11}{30}\\ =>x=\dfrac{11}{8}:\dfrac{11}{30}\\ =>x=\dfrac{11}{8}.\dfrac{30}{11}\\ =>x=\dfrac{30}{8}\\ =>x=\dfrac{15}{4}\\ \dfrac{4}{7}x-\dfrac{1}{3}x+\left(-\dfrac{16}{21}\right)=-\dfrac{2}{3}\\ =>\left(\dfrac{4}{7}-\dfrac{1}{3}\right)x=-\dfrac{2}{3}-\left(-\dfrac{16}{21}\right)\\ =>\left(\dfrac{12}{21}-\dfrac{7}{21}\right)x=-\dfrac{2}{3}+\dfrac{16}{21}\\ =>\dfrac{5}{21}x=-\dfrac{14}{21}+\dfrac{16}{21}\\ =>\dfrac{5}{21}x=\dfrac{2}{21}\\ =>x=\dfrac{2}{21}:\dfrac{5}{21}\)

\(=>x=\dfrac{2}{21}.\dfrac{21}{5}\\ =>x=\dfrac{2}{5}\\ -\dfrac{11}{12}x+\dfrac{15}{2}\left(x+-\dfrac{1}{5}\right)=\dfrac{67}{8}\\ =>-\dfrac{11}{12}x+\dfrac{15}{2}.x-\dfrac{1}{5}=\dfrac{67}{8}\\ =>\left(-\dfrac{11}{12}+\dfrac{15}{2}\right)x=\dfrac{67}{8}+\dfrac{1}{5}\\ =>\left(-\dfrac{11}{12}+\dfrac{90}{12}\right)x=\dfrac{335}{40}+\dfrac{8}{40}\\ =>\dfrac{79}{12}x=\dfrac{343}{40}\\ =>x=\dfrac{343}{40}:\dfrac{79}{12}\\ =>x=\dfrac{343}{40}.\dfrac{12}{79}\\ =>x=\dfrac{343.12}{40.79}\\ =>x=\dfrac{343.3}{10.79}\\ =>x=\dfrac{1029}{790}\)

1: Tìm x

a,  x + 65 = 21

            x = 21 - 65

            x = -44

b, 12 - x = 30

           x = 12 - 30

           x = -18

2) Tính nhanh

SSH : (9-1):1+1= 9 ( số)

TBC:   (9+1):2 = 5]

Tổng là: 9 * 5 = 45

1, tìm x

a, x+ 65 = 67 - 56

=> x + 65 =  11

=> x= -54

vậy x= -54

b, 12 -x =5 x 6

=> 12 - x =30

=> x=-18

vậy x=-18

2, tính nhanh

1+2+3+4+5+6+7+8+9=(1+9)+(2+8)+(3+7)+(4+6)+5

=10 + 10+ 10+ 10+ 5=45

Ta có \(x.a=b\)

\(x=b:a\)

Do đó \(-\frac{3}{5}.x=\frac{5}{6}\)

\(x=\frac{5}{6}:\frac{-3}{5}\)

\(x=-\frac{1}{2}\)

Tương tự 

2. \(x=\frac{6}{8}:\frac{2}{4}=\frac{3}{2}\)

Bạn tự làm câu 3

1.\(\frac{-3}{5}\).x=\(\frac{5}{6}\)

x=\(\frac{5}{6}\):\(\frac{-3}{5}\)

x=\(\frac{-25}{18}\)

2.\(\frac{2}{4}\):x=\(\frac{6}{8}\)

\(\frac{1}{2}\):x=\(\frac{3}{4}\)

x=\(\frac{1}{2}\):\(\frac{3}{4}\)

x=\(\frac{2}{3}\)

3.\(\frac{67}{89}\).x=\(\frac{12}{13}\)

x=\(\frac{12}{13}\):\(\frac{67}{89}\)

x=\(\frac{1068}{871}\)

K MIK NHÉ