Z^2 - 6z+9=0 Factor and solve

Factor because if we have

yz=0 then we can assume y and/or z=0

so factor

so the easiest way is to find what 2 numbers add to - 6 and multiply to get 9 so

we know that they must be both - because we must have x+x = (-) and x^2 = + so therefor they must be negative

factors of 9=3 and 3 so

-3 and - 3

-3+-3=-6 perfect

(z-3) (z-3) = 0

set each to zero

z-3=0

add 3

z=3

z=3 is the answer