The length of a rectangle is the width minus 3 units. The area of the rectangle is 18 units. What is the width, in units, of the rectangle?

Question

This is a math question I have.

Answer 1

Anuj,

 

First things first. L = width minus 3, or l = w-3

Area = length * width  Put in what we know

18 = (w-3) w

18 = w^2 -3w

0 = w^2 - 3w -18  Probably the only way you know to solve a quadratic equation is to set it equal to zero, factor, set each factor to zero, and solve.  For the factoring, since the lead coefficient is 1, we are simply factoring -18 to add to -3.  The numbers are 3 and -6

(w + 3) (w - 6) = 0

Set each factor to zero, ignore the extraneous root which is the negative number, and you have w.  Subtract three from that and you will have l.

You can do it!

Mary