Solving a word problem using a quadratic equation with rational roots

The length of a rectangle is 4 ft less than three times the width, and the area of the rectangle is 55 ft . Find the dimensions of the rectangle. At 00 Length : X 5 Width : I ftAn aircraft factory manufactures airplane engines. The unit cost C (the cost in dollars to make each airplane engine) depends on 2 the number of engines made. If x engines are made, then the unit cost is given by the function C (x) =x 360x+ 37,657. What is the minimum unit cost? Do not round your answer. Unit cost: $l: X S