Original formula = a 2+6a+9-9+8

=(a^2+6a+9)- 1

=(a+3)^2- 1

=(a+3+ 1)(a+3- 1)

=(a+4)(a+2)

2.

x^2-8x-9=0

x^2-8x+ 16- 16-9=0

(x^2-8x+ 16)-25=0

(x-4)^2-25=0

(x-4+5)(x-4-5)=0

(x+ 1)(x-9)=0

x 1=- 1

x2=9