Đáp án:
`a)-31/12`
`b)-2/35`
`c)-99/91`
`d)1/9`
Giải thích các bước giải:
`a)-4/(9).3+7/(6).(-15)/14`
`=-12/9+7/(6).(-15)/14`
`=-12/9+(7.(-15))/(6.14)`
`=-12/9+(-105)/84`
`=-12/9+(-105:21)/(84:21)`
`=-12/9+(-5)/4`
`=(-48)/36+(-45)/36`
`=(-48-45)/36`
`=-93/36`
`=(-93:3)/(36:3)`
`=-31/12`
`b)12/14-4/14-6/7:15/11`
`=12/14-4/14-6/7.(11)/15`
`=(12-4)/14-(6.11)/(7.15)`
`=8/14-66/105`
`=4/7-22/35`
`=20/35-22/35`
`=(20-22)/35`
`=-2/35`
`c)-3/7.(5)/13+(-3)/2.(8)/13`
`=(-3.5)/(7.13)+(-3.8)/(2.13)`
`=-15/91+(-24)/(26)`
`=-15/91+(-12)/13`
`=-15/91+(-12.7)/(91)`
`=-15/91+(-84)/91`
`=(-15-84)/91`
`=-99/91`
`d)(1/9-9/17)+3/6-(8/17-1/2)`
`=(1/9-9/17)+1/2-(8/17-1/2)`
`=1/9-9/17+1/2-8/17+1/2`
`=1/9+(-9/17-8/17)+(1/2+1/2)`
`=1/9+(-9-8)/17+(1+1)/2`
`=1/9+(-17)/17+2/2`
`=1/9+(-1)+1`
`=1/9+0`
`=1/9`