Complete the square

[frctl]

Complete the square and find the standard form of the quadratic function.



My work is the following:



Why is it incorrect?

 

[Dr.Peterson]

You added 9 inside the parentheses, which amounts to adding -9 to the entire expression, since it is multiplied by -1. To balance that, you should have added 9, rather than subtracting 9.

 

[frctl]

Thank you