10 x (x,y) x 10 x 9,9 = 100 x (xx,yy) (xy) x 99 = (xxyy) (10x+y) x 99 = 1000x + 100x + 10y + y 99x + 99y = 1100 + 11y 88y = 110x (88 : 22) x y = (110 : 22) x x 4y = 5x <=> y = 5 ; x = 4
10 x (x,y) x 10 x 9,9 = 100 x (xx,yy) (xy) x 99 = (xxyy) (10x+y) x 99 = 1000x + 100x + 10y + y 99x + 99y = 1100 + 11y 88y = 110x (88 : 22) x y = (110 : 22) x x vậy 4y = 5x <=> y = 5 ; x = 4