\(\frac{2.6.1}{33.24}=\frac{12.1}{33.2.12}=\frac{1}{66}\)

\(\frac{21.4}{9.7.5.3}=\frac{7.3.4}{9.5.7.3}=\frac{4}{45}\)

P/s: Hoq chắc ((:

m = 2/3.5 + 2/5.7 + 2/7.9 + .... + 2/97.99

m= 1/3 - 1/5 + 1/5 - 1/7 + 1/95 - 1/97 + 1/97 - 1/99

m = 1/3 - 1/99

m = 32/99

M= \(\frac{2}{3.5}\) + \(\frac{2}{5.7}\) + \(\frac{2}{7.9}\) + ... + \(\frac{2}{97.99}\)

M= \(\frac{1}{3}\) - \(\frac{1}{5}\) + \(\frac{1}{5}\) - \(\frac{1}{7}\) + \(\frac{1}{7}\) - \(\frac{1}{9}\)+ ...+\(\frac{1}{97}\) - \(\frac{1}{99}\)

M= \(\frac{1}{3}\) - \(\frac{1}{99}\)

M=\(\frac{32}{99}\)

 k cho mình nha!

Ta có :

\(M=\frac{2}{3.5}+\frac{2}{5.7}+...+\frac{2}{97.99}\)

\(=1.\left(\frac{1}{3.5}+\frac{1}{5.7}+...+\frac{1}{97.99}\right)\)

\(=1.\left(\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-...+\frac{1}{97}-\frac{1}{99}\right)\)

\(=1.\left(\frac{1}{3}-\frac{1}{99}\right)\)

\(=1.\frac{32}{99}\)

\(=\frac{32}{99}\)

B=4*13/9*3-4/3*40/9

B=4/3*13/9-4/3*40/9

B=4/3*(13/9-40/9)

B=4/3*(-27)/9

B=4*(-3)/9

B=-4

A=6/7 + 1/7.(2/7+5/7)

A=6/7 + 1/7.7/7=6/7+1/7.1

A=6/7+1/7=7/7=1

M=8/3*2/5*3/8*10*19/2

M=(8/3*3/8)*(2/5*10)*19/2

M=1*4*19/2

M=28

M=\(\frac{1}{1\cdot2}\)- \(\frac{1}{2\cdot3}\)+ \(\frac{1}{2\cdot3}\) - \(\frac{1}{3\cdot4}\) +..........+ \(\frac{1}{10\cdot11}\) - \(\frac{1}{11\cdot12}\)

= \(\frac{1}{2}\) - \(\frac{1}{11\cdot12}\) 

=\(\frac{65}{132}\) 

(17/2+1/2+1).3/5

=10.3/5

=6

có 2 cách làm mà mik làm 1 cách thôi nha !

        A = (6 - 2/3 + 1/2) - (5 + 5/3 - 3/2) - (3 -7/3 + 5/2)

           = ( 36/6 - 4/6 + 3/6 ) - ( 150/30 + 50/30 +45/30 ) - ( 18/6 - 14/6 + 15/6 )

           =          35/6                    -        155/30           -       19/6          = 35/6 - 19/6 - 155/30

          = 16/6 - 155/30 = 80/30 - 155/30 = 75/30 = - 5/2 

Hơi khó nhìn. Chúc hok tốt !

2/5 x 3 + 2/5 x 6 + 2/5

= 2/5 x (3+6+1)

=2/5 x 10

= 20/5=4

`2/5 xx 3 + 2/5 xx 6 +2/5`

`= 2/5 xx 3 + 2/5 xx 6 +2/5 xx1`

`= 2/5xx(3+6+1)`

`= 2/5 xx 10`

`= 20/5`

`=4`

2/5 x 3+2/5x6+2/5

=2/5x\(\left(3+6\right)\)+2/5

=2/5x9+2/5

=2/5x\(\left(9+1\right)\)

=2/5x10

=4

`a,5 xx (-7)+(-2) xx (-5)`

`=5 xx (-7)+5 xx 2`

`= 5 xx (2-7)`

`=5 xx (-5)`

`=-25`

`b,5 xx (-9)+(-2) xx 3`

`=3 xx (-15)+3 xx (-2)`

`=3 xx (-15-2)`

`=3 xx (-17)`

`=-51`

`c,6 xx (-5)^2+3 xx (-15)`

`=2 xx 3 xx 25+3 xx (-15)`

`=3 xx 75-3 xx 15`

`=3 xx (75-15)`

`=3 xx 60`

`=180`

a) 5×(-7) +(-2) ×(-5)

=5.(-7)+2.5

=5.(-7+2)

=5.(-5)=-25