Đáp án:
Giải thích các bước giải:
b1 , a , 4/25 x -13/8 = 4 x -13 / 25 x 8 = 1 x -13 = 25 x 2 = -13 / 50
b , 2,5 : ( -1/9 ) = 2,5 x -9 = -22,5
c , 2/3 + 3/4 x -4/9 = 2/3 + 3 x -4 / 4 x 9 = 2/3 + 1 x -1 / 1 x 3 = 2/3 + -1 /3 = 1/3
d , ( 3 / 4 - 0,2 ) ( -2 / 5 ) = ( 3 / 4 - 1 / 5 ) ( -2 / 5 ) = ( 15 / 20 - 4 / 20 ) ( -2 / 5 ) = 11 / 20 x ( -2 / 5 ) = -11/50
e , -5 / 11 : 7 / 15 x 11 / 5 x ( -30 ) = -5 / 11 x 15 / 7 x 11 / 5 x ( -30 )
= [ ( -5 / 11 ) ( 11/5 ) ] x 15 / 7 x ( -30 )
= -1 x 15/7 x ( -30 ) = -15/7 x ( -30 ) = -450 / 7
f , 6 / 5 x ( -12 / 13 ) + ( -1 / 13 ) x 6 / 5
= 6 / 5 [ ( -12 / 13 ) + ( -1 / 13 ) ]
= 6 / 5 x ( -1 ) = -6 / 5
b2 : a , x x 4/9 = 21 / 22
x = 21 / 22 : 4 / 9
x = 21 / 22 x 9 / 4
x = 189 / 88
b , 12 / 17 : x = 1 / 3
x = 12 / 17 : 1 / 3
x = 12 / 17 x 3
x = 36 / 17
c , -4 / 5 + 5 / 2 x = -3 / 10
5 / 2 x = -3 / 10 - ( -4 / 5 ) = -3 / 10 + 8 / 10 = 5 / 10 = 1 / 2
x = 1 / 2 : 5 / 2 = 1 / 2 x 2 / 5 = 1 / 5
d , 4 / 3 + 5 / 8 : x = 1 / 12
5 / 8 : x = 1 / 12 - 4 / 3 = 1 / 12 - 16 / 12 = -15 / 12 = -5 / 4
x = 5 / 8 : -5 / 4 = 5 / 8 x 4 / -5
x = -1 /2
