Answer
$9y^{2n}-3y^n-10$
Work Step by Step
Consider the given polynomial
$(6y^{2n}+y^n+5)+(3y^{2n}-4y^n-15)$
Need to drop the parentheses.
Thus,
$(6y^{2n}+y^n+5)+(3y^{2n}-4y^n-15)=6y^{2n}+y^n+5+3y^{2n}-4y^n-15$
or, $=6y^{2n}+3y^{2n}+y^n-4y^n+5-15$
or, $=9y^{2n}-3y^n-10$
