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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
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)65 . ( - 101 )
=65.(−100−1)=65.(−100−1)
=65(−100)−65.1=65(−100)−65.1
=−6500−65=−6500−65
=−6565
b)
thank you:)
a.(-65).(100+1)=[(-65).100]+1=(-6500)+1=-6499
b.87.(-99)=87.[(-99)+(-1)]=87.(-1000)=-87000
ơ???
mà lm hộ luôn câu b ik bn:(
b.87.(-99)
=87.[(-99)+(-1)]-1
=87.(-1000)-1
=-87000-1
=86999