This question is and algebra question

Question

the width of a rectangular slab of concrete is 4 m less than the length. The area is 45 meters squared. What are the dimensions of the rectangle

Answer 1

By assumptions we have that if x is the length and y the width then xy=45 and y=x-4. Thus, we obtain the equation x(x-4)=45 or x^2-4x-45=0 which has two solutions, one positive and one negative. Since x represents length it must be positive. So x=9 and y=5.