Bài 16:

a) \(-76\cdot11=-76\left(10+1\right)=-76\cdot10-76\cdot1=-760-76=-836\)

b) \(65\cdot\left(-101\right)=-65\cdot\left(100+1\right)=-65\cdot100-65\cdot1=-6500-65=-6565\)

Bài 17

a) 3x-(-36)=-27

\(\Leftrightarrow3x+36+27=0\)

\(\Leftrightarrow3x+63=0\)

\(\Leftrightarrow3x=-63\)

hay x=-21

Vậy: x=-21

b) Ta có: \(\left|x+25\right|-12=27\)

\(\Leftrightarrow\left|x+25\right|=39\)

\(\Leftrightarrow\left[{}\begin{matrix}x+25=39\\x+25=-39\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=14\\x=-64\end{matrix}\right.\)

Vậy: \(x\in\left\{14;-64\right\}\)

a: \(\left(-34\right)\cdot11\)

\(=-34\left(10+1\right)\)

\(=-34\cdot10-34\cdot1=-340-34=-374\)

b: \(250\cdot\left(-21\right)\)

\(=-250\left(20+1\right)\)

\(=-250\cdot20-250\cdot1=-5000-250=-5250\)

c: \(\left(-23\right)\cdot101\)

\(=\left(-23\right)\left(100+1\right)\)

\(=-23\cdot100-23\cdot1=-2300-23=-2323\)

d: \(31\cdot\left(-99\right)=-31\cdot99\)

\(=-31\left(100-1\right)\)

\(=-31\cdot100+31\cdot1\)

=-3100+31

=-3069

a)=-374                   b)=-5250

c)=-2323                  d)=-3069

a ) - 57 . 11

= ( - 57 ) . ( 10 + 1 )

= [ ( - 57 ) . 10 ] + [ ( - 57 ) . 1 ]

= - 570 + - 57

= - 627

b ) 75 . ( - 21 )

= 75 . [ ( - 20) + ( -  1) ]

= [ 75 . ( - 20 ] + [ 75 . ( - 1 ) ]

= ( - 1500) + ( - 75 )

= - 1575