If using the method of completing the square to solve the quadratic equation x^2+15x+21=0, which number would have to be added to "complete the square"?

What is an equation of the line that passes through the point (-2,3) and is parallel to the line whose equations is y=3/2x-4? i am stuck between y=3/2x or y=3/2x+6 : (

Determine the relationship of ab and cd given the following points

Solve 3x-18=2y and 5x-6y=14 by elimination or substitution . show all !