math
posted by Chad .
The length of a rectangle is 2 cm more than three times the width. Find the dimensions of this rectangle if the area is 21 cm^2.
I know the answer is 9 & 2 1/3 but I found it by trial and error. Is there an easier way to find the answer to this question? Thanks!

the answer can be found by using algebra.
L = 3W + 2
L*W = 21
(3W+2)*W = 21
3w^2 + 2W 21 = 0
(3W 7)(W +3) = 0
W = 7/3
Ignore the negative root