Bài 1:
`a)-286-(54-75)`
`=-286-(-21)`
`=-286+21`
`=-265`
`b)3^5:3³-(5²-2²)+(-20)`
`=3²-(25-4)+(-20)`
`=9-21+(-20)`
`=(-12)+(-20)`
`=-32`
`c)7/36-8/(-9)+(-2)/3`
`=7/36+8/9+(-2)/3`
`=7/36+32/36+(-24)/36`
`=15/36`
`=5/12`
`d)(-12)/18-32/45+5/15`
`=(-2)/3-32/45+1/3`
`=(-30)/45-32/45+15/45`
`=(-47)/45`
`e)(-47).169+31.(-47)`
`=(-47).(169+31)`
`=(-47).200`
`=-9400`
`f)(1/9-9/17)+3/6-(8/17-1/2)+5/9`
`=1/9-9/17+3/6-8/17+1/2+5/9`
`=(1/9+5/9)+(-9/17-8/17)+(3/6+1/2)`
`=2/3+(-17)/17+(3/6+3/6)`
`=2/3+(-1)+1`
`=2/3`
`g)7/13+(-9)/23+1/3+6/13-14/23`
`=(7/13+6/13)+((-9)/23-14/23)+1/3`
`=13/13-23/23+1/3`
`=1-1+1/3`
`=1/3`
Bài 2:
`a)-16-(35-x)=-7`
`35-x=-16-(-7)`
`35-x=-16+7`
`35-x=-9`
`x=35-(-9)`
`x=35+9`
`x=44`
`b)79-|x+8|=-78`
`→|x+8|=79-(-78)`
`→|x+8|=79+78`
`→|x+8|=157`
`→`\(\left[ \begin{array}{l}x+8=157\\x+8=-157\end{array} \right.\)
`→`\(\left[ \begin{array}{l}x=157-8\\x=-157-8\end{array} \right.\)
`→`\(\left[ \begin{array}{l}x=149\\x=-165\end{array} \right.\)
`c)x/4=(-24)/32`
`→x.32=(-24).4`
`→x.32=-96`
`→x=(-96):32`
`→x=-3`
`d)7/18-8/9-x=5/2`
`→7/18-16/18-x=5/2`
`→-1/2-x=5/2`
`→x=-1/2-5/2`
`→x=-6/2`
`→x=-3`
`e)(x+1)/(-12)=(-3)/(x+1)`
`→(x+1).(x+1)=(-3).(-12)`
`→(x+1)²=36`
`→(x+1)²=6²`
`→`\(\left[ \begin{array}{l}x+1=6\\x+1=-6\end{array} \right.\)
`→`\(\left[ \begin{array}{l}x=6-1\\x=-6-1\end{array} \right.\)
`→`\(\left[ \begin{array}{l}x=5\\x=-7\end{array} \right.\)
