Medal true or false the coefficient of x^k y^n-k in the expansion of (x+y)^n equals (n-k / k),

The statement The coefficient of x^k y^n-k in the expansion of (x+y)^n equals (n-k / k) is true.  This will show the standard formula and the expansion of it. We all know that it can still be expanded based on the power or degree of the terms.

What's the denominator