[tex] \frac{9}{x+7} [/tex]⇒x+7∈D₉={1,3,9} (in cazul in care nu stii multimea numerelor intregi Z--nu ati invatat si stii doar multimea numerelor naturale N)
x+7=1 x+7=3 x+7=9
x=1-7=-6∉N x=3-7=-4∉N x=9-7=2
x∈{2}
[tex] \frac{9}{x+7} [/tex]⇒x+7∈D₉={1,-1,3,-3,9,-9} (IN CAZUL IN CARE O STII)
x+7=1 x+7=-1 x+7=3;x=-4 x+7=9;x=2
x=1-7=-6 x=-1-7=-8 x+7=-3;x=-10 x+7=-9;x=-16
x∈{-6,-8,-4,-10,2,-16}