Đáp án:
Giải thích các bước giải:
Bài 7:
a) `-2/3a + 1/2 = 1/5 - 1/-15`
`=> -2/3a + 1/2 = 4/15`
`=> -2/3a = 4/15 - 1/2`
`=> -2/3a = -7/30`
`=> a = -7/30 : -2/3`
`=> a = -7/30 . -3/2 = -7/20`
Vậy `a = -7/20`
b) `7/26 + -1/13 = 21/13a`
`=> 7/26 - 2/26 = 21/13a`
`=> 21/13a = 5/26`
`=> a = 5/26 : 21/13`
`=> a = 5/26 . 13/21 = 5/42`
Vậy `a = 5/42`
c) `3/4a - 1/2 = 3/7`
`=> 3/4a = 3/7 + 1/2`
`=> 3/4a = 13/14`
`=> a = 13/14 : 3/4`
`=> a = 13/14 . 4/3 = 26/21`
Vậy `a = 26/21`
Bài 8:
b) `(-3x + 7)(-3x + 1/2) = 0`
TH1: `-3x + 7 = 0`
`=> -3x = 0 - 7 = -7`
`=> x = -7 : -3 = 7/3`
TH2: `-3x + 1/2 = 0`
`=> -3x = 0 - 1/2 = -1/2`
`=> x = (-1/2) : (-3) = 1/2 . 1/3 = 1/6`
Vậy `x = 7/3 ; x = 1/6`
Học tốt. Nocopy.
