Question

Tính hợp lí ( Giúp mk với )

A = (-4/5 + 4/3) + (-5/4 + 14/5) - 7/3

B = 8/3 x 2/5 x 3/8 x 10 x 19/92

C = -5/7 x 2/11 + (-5)/7 x 9/14 + 1/57

D = 12/19 x 7/15 x (-13)/17 x 19/12 x 17/13

E = 1/1x2  +   1/2x3   + 1/3x4  + ....+ 1/49 x 50

 

 

Answer 1

A = ( -4/5 + 4/3 ) + (-5/4 + 14/5) - 7/3

  =   8/15 + 31/20 - 7/3

  =  25/12 - 7/3

  = -1/4

B = 8/3 x 2/5 x 3/8 x 10x 19/92

   = 16/15 x 15/4 x 19/92

   = 4x19/92

   = 19/23

Answer 2

C = - \(\dfrac{5}{7}\) x \(\dfrac{2}{11}\) + \(\dfrac{-5}{7}\) x \(\dfrac{9}{14}\) + \(\dfrac{1}{57}\)

   = - \(\dfrac{10}{77}\) - \(\dfrac{45}{98}\) + \(\dfrac{1}{57}\)

  = - \(\dfrac{635}{1078}\) + \(\dfrac{1}{57}\)

 = - \(\dfrac{36195}{61446}\) + \(\dfrac{1078}{61446}\)

 = - \(\dfrac{35117}{61446}\)

 

 

 

Answer 3

D = \(\dfrac{12}{19}\) x \(\dfrac{7}{15}\) x \(\dfrac{-13}{17}\) x \(\dfrac{19}{12}\)  x \(\dfrac{17}{13}\)

D =  (\(\dfrac{12}{19}\) x \(\dfrac{19}{12}\)) x (- \(\dfrac{13}{17}\) x \(\dfrac{17}{13}\)) x \(\dfrac{7}{15}\)

D =   1  x  (- 1) x \(\dfrac{7}{15}\)

D = -1 x \(\dfrac{7}{15}\)

D = - \(\dfrac{7}{15}\)

Answer 4

E = \(\dfrac{1}{1.2}\) + \(\dfrac{1}{2.3}\) + \(\dfrac{1}{3.4}\) + ... + \(\dfrac{1}{49.50}\)

E = \(\dfrac{1}{1}\) - \(\dfrac{1}{2}\) + \(\dfrac{1}{2}\) - \(\dfrac{1}{3}\) + \(\dfrac{1}{3}\) + \(\dfrac{1}{4}\) + ... + \(\dfrac{1}{49}\) - \(\dfrac{1}{50}\)

E = \(\dfrac{1}{1}\) - \(\dfrac{1}{50}\)

E = \(\dfrac{49}{50}\)