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a: =235-235+43+57=100
b: =82(-136-37)
=-173*82=-14186
c: =-5/15+12/15=7/15
d: =-33/18+10/18+17/12
=-23/18+17/12
=-46/36+51/36=5/36
Bài làm:
Ta có: \(\left(x+9\right)+\left(x+10\right)+\left(x+11\right)+...+\left(x+18\right)=235\)
\(\Leftrightarrow\left(x+x+...+x\right)+\left(9+10+...+18\right)=235\)
\(\Leftrightarrow10x+\frac{\left(9+18\right).10}{2}=235\)
\(\Leftrightarrow10x+135=235\)
\(\Leftrightarrow10x=100\)
\(\Rightarrow x=10\)
Vậy x = 10
g = 9
\(\left(x+9\right)+\left(x+10\right)+\left(x+11\right)+...+\left(x+18\right)=235\)
\(\Leftrightarrow\left(x+x+x+...+x\right)+\left(9+10+11+...+18\right)=235\)
\(\Leftrightarrow\left(x+x+x+...+x\right)+\frac{\left(18+9\right)\times\left[\left(18-9\right):1+1\right]}{2}=235\)
\(\Leftrightarrow10x+135=235\)
\(\Leftrightarrow10x=100\)
\(\Leftrightarrow x=100:10=10\)
a, A= x + (-37) - 235 = (-11) + (-37) - 235 = -48 - 235 = -283
b, A = x + (-37) - 235 = 187 - 37 - 235 = 150 - 235 = -85
\(2x+12-3x=-21\)
\(x.\left(2+12-3\right)=-21\)
\(x.11=-21\)
\(x=-\frac{21}{11}\)
\(\dfrac{3x}{2\cdot5}+\dfrac{3x}{5\cdot8}+\dfrac{3x}{8\cdot11}+\dfrac{3x}{11\cdot14}=\dfrac{1}{21}\\ x\cdot\left(\dfrac{3}{2\cdot5}+\dfrac{3}{5\cdot8}+\dfrac{3}{8\cdot11}+\dfrac{3}{11\cdot14}\right)=\dfrac{1}{21}\\ x\cdot\left(\dfrac{1}{2}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{8}+\dfrac{1}{8}-\dfrac{1}{11}+\dfrac{1}{11}-\dfrac{1}{14}\right)=\dfrac{1}{21}\\ x\cdot\left(\dfrac{1}{2}-\dfrac{1}{14}\right)=\dfrac{1}{21}\\ x\cdot\dfrac{3}{7}=\dfrac{1}{21}\\ x=\dfrac{1}{21}:\dfrac{3}{7}\\ x=\dfrac{1}{9}\)
3x = 11 + 235
3x = 246
x = 82
3x-235=11
3x=11+235
3x=246
=>x=246:3=82