Can anyone tell me the difference between the two lines below? I am getting different results but I expected them to produce similar results.

double lhs=y*log10(x);
double rhs=x*log10(y);

------------------------------ double lhs=log10(x); double rhs=log10(y); lhs*=y;

rhs*=x;

------------------------------ I am getting wrong answers for x=6,y=6 while submitting on codeforces but I am getting correct on VSCode.