bài 1:tìm x a)-5x + 1=7 b)/x-1/-2=3 c)4.(x-8)=-30 +(-10) Bài 2 :tính nhanh a)26.(19-13)-19.(26-13) b)15.81+(-85).(-81) c) ( -13).27+13.(-73)

Bài 1:

`a,-5x+1=7`

`⇔-5x=7`

`⇔x=7/-5`

`b,|x-1|-2=3`

`|x-1|=5`

`⇒`$\left[ \begin{array}{l}x-1=5\\x-1=-5\end{array} \right.$ 

`⇒`$\left[ \begin{array}{l}x=6\\x=-4\end{array} \right.$ 

 Vậy `x=-4` hoặc `x=6`

`c,4(x-8)=-30+(-10)`

`4x-32=-40`

`⇔4x=-8`

`⇔x=-2`

bài 2:

`a,26.(19-13)-19.(26-13)`

`=26.19-26.13-19.26+19.13`

`=(26.19-19.26)+13.[(-26)+19]`

`=0+13.(-7)`

`=-91`

`b,15.81+(-85).(-81)`

`=15.81+85.81`

`=81.(15+85)`

`=81.100`

`=8100`

`c,(-13).27+13.(-73)`

`=13.(-27)+13.(-73)`

`=13.[(-27)+(-73)]`

`=13.(-100)`

`=-1300`

~ Học tốt ~