this is what i have left but i don't know how to finish it.

Question

THe length of a rectangle is 1cm more than 4 times its width. if the area of the rectangle is 74cm^2, find the dimensions of the rectangle to the nearest thousandsth.

so then:

a =Lw
A = 74
W= W
L=4W+1

FROM ALL THIS I END UP WITH

0 = 4W^2+W-74
THEN I USED THE QUADRATIC EQUATION

AND I AM IN THIS STEP:

X=(-1 +/- sqrt 1185)/(8) from here is what i don't know .

It's really simple. If you follow thw steps i showed you in your previous question you'll get it. You have the right values, not just do the math.
-1 minus sqrt(1185)/8 and -1 plus sqrt(1185)/8. Obviously your negative answer is the wrong one

i get this:

width : 4.2cm
length: 17.8cm