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a) \(x+15=18-\left(-27\right)\)
\(\Leftrightarrow x+15=18+27\)
\(\Leftrightarrow x+15=45\)
\(\Leftrightarrow x=45-15\)
\(\Leftrightarrow x=30\)
b) \(-x+7=28\)
\(\Leftrightarrow-x=28-7\)
\(\Leftrightarrow-x=21\)
\(\Leftrightarrow x=-21\)
c) \(20-\left(-x\right)=14\)
\(\Leftrightarrow20+x=14\)
\(\Leftrightarrow x=14-20\)
\(\Leftrightarrow x=-6\)
d) \(2x+5=x-14\)
\(\Leftrightarrow2x+5-\left(x-14\right)=0\)
\(\Leftrightarrow2x+5-x+14=0\)
\(\Leftrightarrow x+19=0\)
\(\Leftrightarrow x=0-19\)
\(\Leftrightarrow x=-19\)
e) \(x+17=-8-20\)
\(\Leftrightarrow x+17=-\left(8+20\right)\)
\(\Leftrightarrow x+17=-28\)
\(\Leftrightarrow x=-28-17\)
\(\Leftrightarrow x=-\left(28+17\right)\)
\(\Leftrightarrow x=-45\)
f) \(3x+15=2x+6\)
\(\Leftrightarrow3x+15-\left(2x+6\right)=0\)
\(\Leftrightarrow3x+15-2x-6=0\)
\(\Leftrightarrow x+9=0\)
\(\Leftrightarrow x=0-9\)
\(\Leftrightarrow x=-9\)
1)tính
a)\(-17+\left(-19\right)+25\)
\(=-17-19+25\)
\(=-\left(17+19\right)+25\)
\(=-36+25\)
\(=-\left(36-25\right)\)
\(=-11\)
b)\(-26+\left(-25\right)-18\)
\(=-26-25-18\)
\(=-\left(26+25\right)-18\)
\(=-51-18\)
\(=-\left(51+18\right)\)
\(=-69\)
c)\(35-\left(-19\right)-19-8\)
\(=35+19-19-8\)
\(=35+\left(19-19\right)-8\)
\(=35+0-8\)
\(=35-8\)
\(=27\)
d)\(1963-\left(-180\right)-1990\)
\(=1963+180-1990\)
\(=2143-1990\)
\(=153\)
2)Tìm x thuộc z biết
a)\(x-\left(-18\right)=25+\left(-17\right)\)
\(\Leftrightarrow x+18=25-17\)
\(\Leftrightarrow x+18=8\)
\(\Leftrightarrow x=8-18\)
\(\Leftrightarrow x=-10\)
Vậy x=-10
b)\(x-28=-27-30\)
\(\Leftrightarrow x-28=-\left(27+30\right)\)
\(\Leftrightarrow x-28=-57\)
\(\Leftrightarrow x=-57+28\)
\(\Leftrightarrow x=-\left(57-28\right)\)
\(\Leftrightarrow x=-29\)
Vậy x=-29
c)\(35-\left(-x\right)=27-18-\left(-8\right)\)
\(\Leftrightarrow35+x=27-18+8\)
\(\Leftrightarrow35+x=9+8\)
\(\Leftrightarrow35+x=17\)
\(\Leftrightarrow x=17-35\)
\(\Leftrightarrow x=-18\)
Vậy x=-18
d)\(40+\left(-x\right)=35-\left(-27\right)\)
\(\Leftrightarrow40-x=35+27\)
\(\Leftrightarrow40-x=62\)
\(\Leftrightarrow x=40-62\)
\(\Leftrightarrow x=-22\)
Vậy x=-22
1a)1+2+3+...+x=0
\(\frac{x.\left(x+1\right)}{2}\)=0
x.(x+1) =0:2
x.(x+1) =0
x.(x+1) =0.1
vây x=0
tich dung cho minh nha
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
1c)
-x-27=-2x+50
-x+2x=50+27
x=77
1d)
3(x+2)=2x-16
3x+6=2x-16
3x-2x=-16-6
x=-22
2a)
a+5=20
a=20-5
a=15
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
3a)
17-(-40)+38
=17+40+38
=57+38
=95
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)\(208-109-63-\left(-80\right)\)
\(=208-109-63+80\)
\(=99-63+80\)
\(=36+80\)
\(=116\)
like mạnh