Đáp án + Giải thích các bước giải:
Bài 5.8
a) `(x + 1)/6 = (-1)/2 =>x+1=(-1)/2*6=-3=> x+1=-3`$\\$ `=> x = -3 - 1 = -4`
`b) (x - 2)/10 = 3/15 => (x-2)/10 = 1/5` $\\$ `=> x-2=1/5*10=>x-2=2=>x=4`
`c)x/15=4/10 =>x/15=2/5=>x=2/5*15=2/1*3=6`
`d) (x - 3)/49 = (-2)/7 => x-3=(-2)/7*49` $\\$ `=> x - 3 = (-2)/1*7=-14` $\\$ `=> x = -14 + 3 = -11`
Bài 9.6 :
`a)x - 3/4 = 1/7 => x = 1/7 +3/4` $\\$ `=> x = 4/28 + 21/28 = 25/28`
`b)(-x+3/5)+13/20=5/6 => (-x+3/5)=5/6-13/20` $\\$ `=> -x+3/5=50/60-39/60` $\\$ `=> -x+3/5 = 11/60` $\\$ `=> -x = 11/60 - 3/5 = -5/12` $\\$ `=> x= 5/12`
`c)x/2-2/5=1/10=>(5x)/10 - 4/10 = 1/10` $\\$ `=> 5x - 4 = 1 => 5x = 5 => x = 1`
`d) 15/x-1/3=28/51` $\\$ `=> 15/x = 28/51 + 1/3 = 15/17` $\\$ `=> x = 17`
Bài 10.3 :
`a) 2/3+1/5*10/7 = 2/3+1/1*2/7=2/3+2/7=14/21+6/21=20/21` $\\$ `b) 7/12 - 27/7*1/18 = 7/12-3/7*1/2=7/12-3/14 = 31/84` $\\$ `c) (23/41-15/82)*41/25=(46/82-15/82)*41/25=31/82*41/25=31/2*1/25=31/50` $\\$ `d) (4/5+1/2)(3/13-8/13) = 13/10*(-5)/13=(-5)/10=(-1)/2`
