2x+x+x+2y times 3y times y

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

Bring the fraction a/a-4 to a denominator of 16-a^2

Which geometric principle is used to justify the construction below?