Please help guys one question

Factor completely. 4p^2 + 36p + 81 express the answer in the form (ap + b)^2

What number should be added to both sides of the equation to complete this square? x^2-10x=7

Kapil needed to buy a long wooden beam. he went to two sawmills that each charge an initial fee plus an additional fee for each meter of wood. the following equation gives the price (in dollars) of a wooden beam from the first sawmill as a function of its length (in meters). p = 5+20xp=5+20x