Ответ:

8. 3

9. 0

Объяснение:

8. (y-2)(y+3)-(y-2)^2=5

(y-2)(y+3)-(y-2)^2-5=0

y^2+3y-2y-6-(y^2-2*2*y+4)-5=0

y^2+3y-2y-6-y^2+2*2*y-4-5=0

5y-15=0

5y=15 |:5

y=3

9. (n+1)^2-(n-1)^2

(n+1)^2-(n-1)^2=0

n^2+2n+1-(n^2-2n+1)=0

n^2+2n+1-n^2+2n-1=0

4n=0

n=0