Question

Aratati ca: a*xy cu bara deasupra+b*yx cu bara deasupra=ab cu bara deasupra*x+ba cu bara deasupra*y cu a,b,x,y cifre nenule

Answer 1

a* (10x+y) +b*(10y+x)=(10a+b)*x+(10b+a)*y
10ax+ay+10by+bx= 10ax+bx+10by+ay

Answer 2

xy * a+ yx* b=ab *x+ba  * y
(10x+y) *a+(10y+x)*b=(10a+b) * x+ (10 b+ a) * y
(11x+11y) *a*b=(11a+11b) * x *y
10x+10y=10a+10b
10(x+y)=10(a+b)