1) Tìm x thuộc z biết
a) \(x+18=2x+35\)
\(\Leftrightarrow x+18-\left(2x+35\right)=0\)
\(\Leftrightarrow x+18-2x-35=0\)
\(\Leftrightarrow-x-17=0\)
\(\Leftrightarrow-x=17\)
\(\Leftrightarrow x=-17\)
b) \(x+80=-45-27\)
\(\Leftrightarrow x+80=-\left(45+27\right)\)
\(\Leftrightarrow x+80=-72\)
\(\Leftrightarrow x=-72-80\)
\(\Leftrightarrow x=-\left(72+80\right)\)
\(\Leftrightarrow x=-152\)
c) \(-x-27=-2x+50\)
\(\Leftrightarrow-x-27-\left(-2x+50\right)=0\)
\(\Leftrightarrow-x-27+2x-50=0\)
\(\Leftrightarrow x-77=0\)
\(\Leftrightarrow x=77\)
d) \(3\left(x+2\right)=2x-16\)
\(\Leftrightarrow3\left(x+2\right)-\left(2x-16\right)=0\)
\(\Leftrightarrow3x+6-2x+16=0\)
\(\Leftrightarrow x+22=0\)
\(\Leftrightarrow x=-22\)
3) Tính
a)\(17-\left(-40\right)+38\)
\(=17+40+38\)
\(=57+38\)
\(=95\)
b)\(208-109-63-\left(-80\right)\)
\(=208-109-63+80\)
\(=99-63+80\)
\(=36+80\)
\(=116\)
