a/ \(a+3\inƯ\left(7\right)\)
\(Ư\left(7\right)=\left\{\pm1;\pm7\right\}\)
\(\Rightarrow a\in\left\{-10;-4;-2;4\right\}\)
b/ \(2a\inƯ\left(-10\right)\)
\(Ư\left(-10\right)=\left\{\pm1;\pm2;\pm5;\pm10\right\}\)
\(\Rightarrow a\in\left\{-5;-1;1;5\right\}\)do \(a\inℤ\)
c/ \(a+1\inƯ\left(3a+7\right)\Rightarrow3a+7⋮a+1\)
\(\Rightarrow3a+7-3\left(a+1\right)⋮a+1\)
\(\Leftrightarrow4⋮a+1\)
\(Ư\left(4\right)=\left\{\pm1;\pm2;\pm4\right\}\)
\(\Rightarrow a\in\left\{-5;-3;-2;0;1;3\right\}\)
d/ \(2a+1\inƯ\left(3a+5\right)\Rightarrow3a+5⋮2a+1\)
\(\Rightarrow3a+5-\left(2a+1\right)⋮2a+1\)
\(\Leftrightarrow a+4⋮2a+1\)
\(\Rightarrow2\left(a+4\right)⋮2a+1\Leftrightarrow2a+8⋮2a+1\)
\(\Rightarrow2a+8-\left(2a+1\right)⋮2a+1\Leftrightarrow7⋮2a+1\)
\(Ư\left(7\right)=\left\{\pm1;\pm7\right\}\)
\(\Rightarrow a\in\left\{-4;-1;0;3\right\}\)
thank you bạn lê đức anh
