Question

complete the square:
x^2 + 14x

Answer 1

Use for d:
\[\LARGE (\frac{b}{2a})^2\]

Answer 2

This is actually pretty simple.
To complete the square, you need the coefficient of the x^2 term to be 1.
Here it is 1 already.
Then all you need to do is take the coefficient of the x-term, divide it by 2, and square it.