You have the following expression:
(6 - 5i)(6 - 5i)
In order to simplify the previous expression, you proceed as follow:
(6 - 5i)(6 - 5i) apply distribution property
= 6(6) - 5i(6) + 6(-5i) -5i(-5i)
= 36 - 30i - 30i + 25i² simplify
= 36 - 60i + 25i²
Furthermore, you take into account the following identity for i²:
i =√(-1)
i² = -1
Then, by replacing the previous expression for i² you have:
36 - 60i + 25i²
= 36 - 60i + 25(-1)
= 36 - 60i - 25
= 36 - 25 - 60i
= 11 - 60i
Hence, the simplified expression is 11 - 60i