Question 161830
Area = 4x^3-5x^2-10x-3 and width = 4x+3
(4x^3-5x^2-10x-3)/(4x+3)=(x^2-2x-1) is the length.
This requires long division which is very clumbersome to present here.
Proof:
x^2-2x-1
4x+3 (multiply)
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4x^3-8x^2-4x+3x^2-6x-3
4x^3-5x^2-10x-3