c. 4/7 : (-2) + 3/7
= -2/7 + 3/7
= 1/7
d. 1/3 . 4/5 + 1/3 . 6/5 - 1/3
= 1/3 . (4/5 + 6/5 - 1)
= 1/3 . 1
= 1/3
e. 3/7 . 9/26 - 1/14 . 1/13
= 27/182 - 1/182
= 1/7
f. -5/7 . 2/11 + 9/27 . (-5/11) + 12/7
= -10/77 - 5/33 + 12/7
= 331/231
Bài 2:
a. x : 3/4 + 1/4 = 2
x : 3/4 = 2 - 1/4
x : 3/4 = 7/4
x = 7/4 . 3/4
x = 21/16
Vậy x = 21/16
b. 4/5 . x + 1/5 = -1
4/5 . x = -1 - 1/5
4/5 . x = -6/5
x = -6/5 : 4/5
x = -3/2
Vậy x = -3/2
c. 3/4 : x + 1/2 = -2
3/4 : x = -2 - 1/2
3/4 : x = -5/2
x = 3/4 : (-5/2)
x = -3/10
Vậy x = -3/10
d. 4/5 : 2x = -7
2x = 4/5 : (-7)
2x = -4/35
x = -4/35 : 2
x = -2/35
Vậy x = -2/35
e. |2x - 1/4| = 3
Trường hợp 1:
2x - 1/4 = 3
2x = 3 + 1/4
2x = 13/4
x = 13/4 : 2
x = 13/8
Trường hợp 2:
2x - 1/4 = -3
2x = -3 + 1/4
2x = -11/4
x = -11/4 : 2
x = -11/8
Vậy x = 13/8 hoặc x = -11/8
f. |x² + 1/2| = 3/2
Trường hợp 1:
x² + 1/2 = 3/2
x² = 3/2 - 1/2
x² = 1
x = 1 hoặc x = -1
Trường hợp 2:
x² + 1/2 = -3/2
x² = -3/2 - 1/2
x² = -2
x = √2 hoặc x = -√2
