1) tính giá trị biểu thức bằng cách hợp lí A=5/11.5/7+5/11.2/7+6/11 B=3/13.6/11+3/13.9/11-3/13.4/11 C= (12/61-31/21+14/91) .

2 bình luận về “1) tính giá trị biểu thức bằng cách hợp lí A=5/11.5/7+5/11.2/7+6/11 B=3/13.6/11+3/13.9/11-3/13.4/11 C= (12/61-31/21+14/91) .”

1. Bài 1:

   A=5/11 . 5/7+5/11 . 2/7+6/11

   A=5/11 . (5/7+2/7)+6/11

   A=5/11 . 1+6/11

   A=11/11=1

   B=3/13 . 6/11+3/13 . 9/11-3/13 . 4/11

   B=3/13 . (6/11+9/11-4/11)

   B=3/13 . 1

   B=3/13

   C= (12/61-31/21+14/91) . (1/2-1/3-1/6)

   C= (12/61-31/21+14/91) . (3/6-2/6-1/6)

   C=(12/61-31/21+14/91) . 0=0

   Bài 2:

   a)4/7x+2/3=(-1)/5

   4/7x=(-1)/5-2/3

   4/7x=(-13)/15

   x=(-13)/15:4/7=(-91)/60

   Vậy x=(-91)/60

   b)2/9-7/8x=1

   7/8x=1/9

   x=1/9:7/8

   x=8/63

   Vậy x=(8/63)

   c)4/5+7/8:x=1/6

   7/8:x=(-19)/30

   x=7/8:(-19)/30

   x=(-105)/76

   Vậy x=(-105)/76

   d)5/7:x-1=2/3

   5/7:x=5/3

   x=5/7:5/3

   x=3/7

   Vậy x=3/7

   Trả lời
2. Giải đáp:

   1)

   A=5/11. 5/7+ 5/11 . 2/7+6/11

   =5/11(5/7+2/7)+6/11

   =5/11 .1+6/11

   =5/11+6/11

   =1

   B=3/13. 6/11+3/13. 9/11-3/13. 4/11

   =3/13(6/11+9/11-4/11)

   =3/13. 1

   =3/13

   C= (12/61-31/21+14/91) . (1/2-1/3-1/6)

   =(12/61-31/12+14/91).0

   =0

   2)

   a) 4/7 x + 2/3=-1/5

   => 4/7 x =-13/15

   => x=-91/60

   Vậy x=-91/60

   b) 2/9-7/8 x =1

   => -7/8 x =7/9

   => x=-8/9

   Vậy x=-8/9

   c) 4/5 + 7/8 : x =1/6

   => 7/8 . 1/x=-19/30

   => 1/x=-76/105

   =>x=-105/76

   Vậy x=-105/76

   d) 5/7 : x -1=2/3

   => 5/7 . 1/x = 5/3

   => 1/x=7/3

   => x=3/7

   Vậy x=3/7

   @loanluyendh

   Trả lời