it would be f
the first sentence is .
we simplify the left hand side by applying this property to get;
we now rewrite the right hand side too in an index form to obtain;
we now equate the exponents to get;
the second sentence is
we simplify the left hand side first to get;
we now rewrite the left hand side too in index form to obtain;
we equate the exponents to get;
this implies that;
this is the way of writing that equation.