Answer:

i) x²+18x+80

ii) 5²-y²

Step-by-step explanation:

i) (x+a)(x+b)= x²+(a+b)x+ab

(x+8)(x+10)=x²+(8+10)x+8×10

=x²+18x+80

ii) (x-y)(x+y)=(x²+y²)

(5-y)(5+y)=(5²-y²)