Answer
$x^{8}+8x^7y^2+28x^6y^4$
Work Step by Step
Apply Binomial Theorem.
$(a+b)^n=\sum_{r=0}^n\dbinom{n}{r}(a)^{n-r}b^r$
$(x+y^2)^8=\dbinom{8}{0}(x)^8(y^2)^0+\dbinom{8}{1}(x)^7(y^2)^1+\dbinom{8}{2}(x)^6(y^2)^2$
or, $=(1)x^{8}(1)+8(x^7)(y^2)+28x^6y^4$
or, $=x^{8}+8x^7y^2+28x^6y^4$
