1a)
x+18 =2x+35
x-2x=35-18
-x=17
x=-17
1b)
x+80=-45-27
x+80=-72
x=-72-80
x=-152
1d)
3(x+2)=2x-16
3x+6=2x-16
3x-2x=-16-6
x=-22
2b)
|a+6|+|a+7|=0
vì |a+6| ≥ 0; |a+7| ≥ 0 ⇒ |a+6|+|a+7|≥0
mà |a+6|+|a+7|=0
⇒|a+6|=0 và |a+7|=0
⇒a+6=0 và a+7=0
⇒a=-6 và a=-7
⇒không có giá trị của a (vì không thể có 2 kết quả của a)
3b)
208-109-63-(-80)
=208-109-63+80
=99-63+80
=36+80
=116
2)Tìm a thuộc Z biết
a) \(a+5=20\)
\(\Leftrightarrow a=20-5\)
\(\Leftrightarrow a=15\)
b)\(\left|a+6\right|+\left|a+7\right|=0\)
\(\Leftrightarrow\left\{{}\begin{matrix}a+6=0\\a+7=0\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}a=-6\\a=-7\end{matrix}\right.\)
c)\(\left|a+3\right|-\left|2a+1\right|=0\)
\(\Leftrightarrow\left\{{}\begin{matrix}a+3=0\\2a+1=0\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}a=-3\\2a=-1\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}a=-3\\a=\dfrac{-1}{2}\left(loai\right)\end{matrix}\right.\)
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)\(208-109-63-\left(-80\right)\)
\(=208-109-63+80\)
\(=99-63+80\)
\(=36+80\)
\(=116\)
