I'm working through some exercises to brush up my pre-calculus algebra and I'm asked to solve several exercises by completing the square (n.b. using the abc-formula isn't allowed for these exercises).

This kind of puzzles me, again: I can't use the abc-formula. The uneven b (7x) doesn't allow for a square, unless I add an x, which would get me something like: , which seems an unfruitful endeavor...

Any tips?