Answer:
81
Step-by-step explanation:
Given the expression: 
To make it a perfect square, we follow the following steps.
Divide the coefficient of x by 2
- Coefficient of x=18, 18/2=9
Square It
Add it to the expression
This is written as a perfect square as: 
The constant term required therefore is 81.
I can’t see good this image
12.9986 would be the answer from a calculator but I'd say it's 12.9. Hope this helped!