Question

Determinati nr nat x si y ,stiind ca xy7(cu bara de asupra)+3· 4xy(cu bara de asupra)=2143

Answer 1

xy7 + 4xy + 4xy + 4xy = 2143
x = 7
y = 2
727 + 3 ·472 = 727 + 1416 = 2143

Answer 2

xy7+3·4xy=2143
⇒100x+10y+7+3·400+10x+y=2143
⇒100x+10y+7+1200+10x+y=2143
⇒110x+11y+1207=2143
⇒110x+11y=936
⇒11·10·x+11·y=936
⇒11[10x+y]=936
⇒10x+y=85,[09];
⇒85,[09]∉N⇔x,y∉N;