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\(a,-12.\left(x-5\right)+7.\left(-x+3\right)=5\)
\(-12x+60-7x+21=5\)
\(-19x+81=5\)
\(-19x=5-81\)
\(-19x=-76\)
\(x=4\)
\(b,30.\left(x+2\right)-6.\left(x-5\right)-24.x=100\)
\(30x+60-6x+30-24x=100\)
\(0x+90=100\)
\(0x=100-90\)
\(0x=10\)
=> ko có giá trị nào thõa mãn x
![](https://rs.olm.vn/images/avt/0.png?1311)
\(x⋮12\Rightarrow x\in B\left(12\right)\)
\(B\left(12\right)=\left\{0;12;24;36;48;60;72;84;...\right\}\)
\(do 13< x< 75\Rightarrow x\in\left\{24;36;48;60;72\right\}\)
b) \(6⋮\left(x-1\right)\Rightarrow x-1\inƯ\left(6\right)\)
\(Ư\left(6\right)=\left\{1;2;3;6\right\}\)
\(\Rightarrow x-1\in\left\{1;2;3;6\right\}\)
\(\Rightarrow x\in\left\{2;3;4;7\right\}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(=0,3-\dfrac{6}{5}+\dfrac{1}{5}.\dfrac{-1}{2}\)
\(=0,3-\dfrac{6}{5}-\dfrac{1}{2}\)
\(=0,3-1,2-0,5\)
\(=-1,4\)
X x 4,5 + 1,5 x X + X x 6
=X x(4,5+1,5+6)
=X x12
Còn lại mik chịu