Answer:
L = 4.5
Explanation:
You can rewrite the equation as 2L^2 + L - 45 = 0 and then solve using the quadratic formula
L = (-1 plus or minus the sq root of 361) / 4
L = (-1 plus or minus 19) / 4
L = -5 or 4.5 but lengths can't be negative so the length is 4.5