GCF of 12z3, 45z2, and 18z5.

  3z^2

Step-by-step explanation:

Factors of the different terms are ...

  12z^3 = 2·2·3·z·z·z

  45z^2 = 3·3·5·z·z

  18z^5 = 2·3·3·z·z·z·z·z

The common factors are 3 and z·z.

The greatest common factor is 3z^2.

in simplified version   it would be x ≤-4

step-by-step explanation:

multiply each term in x ≤-4 by -1

yes because there is exactly one y value for every x value

for function there can't be more than one value for every x value