Question

Gasiti toate nr naturale xy (cu linie sus) mai mari cu 27 decay yx (cu linie sus)

Answer 1

xy= 27+yx

10x+y=27+10y+x

10x-x+y-10y=27

9x-9y=27

9(x-y)=27    :9

(x-y)=3;    x ; y <9, x; y ≠0

(x, y)={(4,1), (5,2), (6,3), (7,4), (8,5), (9,6)}

xy∈{41, 52, 63, 74, 85, 96}