To do this I recommend to do a visual representation of the rectangle. We know that L*W=A. So it’s fair to say that A=640. We know the width is going to be x-4 and Length will be x. Simply use the box method(if you don’t know what that is I suggest you look it up). First make a one column by 2 rows. It’s basically like a Punnet square. Multiply x*x=x^2 and Multiply -4*x=-4x. So it should look like this now. After doing that it gives you your terms: x^2-4x. When doing this don’t forget to make the equation equal to your Area which in this case is 640. If we include the area it should be x^2-4x=640. At this point we can start using the quadratic formula but before we do this you must set the equation to standard form. Once you have identified A,B,C you can now plug that into the formula(In photo 3). Hopefully you can solve the rest. When all of this is done your answer should be:
1290 and -1284
Hope this helped
Good luck!
