Step-by-Step Solution:
Step 1: Identify the perfect squares.
- The first term, [tex]\( z^2 \)[/tex], is the square of [tex]\( z \)[/tex].
- The third term, 81, is the square of 9:
[tex]\[ z^2 = (z)^2 \][/tex]
[tex]\[ 81 = 9^2 \][/tex]
Step 2: Verify the middle term.
- The middle term, [tex]\( 18z \)[/tex], should be 2 times the product of [tex]\( z \)[/tex] and 9:
[tex]\[ 2 \cdot z \cdot 9 = 18z \][/tex]
Since [tex]\( 18z = 2 \cdot z \cdot 9 \)[/tex], we verify that the middle term is correctly formed.
Step 3: Use the perfect square trinomial formula.
- The quadratic expression fits the form [tex]\( A^2 + 2AB + B^2 = (A + B)^2 \)[/tex], where [tex]\( A = z \)[/tex] and [tex]\( B = 9 \)[/tex]:
[tex]\[ z^2 + 18z + 81 = (z + 9)^2 \][/tex]
So, the factored form of the given expression [tex]\( z^2 + 18z + 81 \)[/tex] is:
[tex]\[ (z + 9)^2 \][/tex]
Therefore, the completely factored expression is:
[tex]\[ z^2 + 18z + 81 = (z + 9)^2 \][/tex]