Algebra 2
posted by Kate .
how do I find the length and width of a rectangle when the width of the rectangle is 3 feet less tahn the length. The area is 18ft^2

Here is how to get the answer using algebra.
L*W = L*(L3) = 18
L^2 3L 18 = 0
(L+3)(L6) = 0
L = 6 or 3
Take the positive root for L. A negative length does not make sense in this case.
Then compute W. 
what is an expression for an area of an equilateral triangle,A, as a function of its diameter,d?