Let f be the funtion given by(adsbygoogle = window.adsbygoogle || []).push({}); f(x) = 4x^2 - x^3, let L be the liney = 18 - 3x, where L is tangent to the graph of f.

Show that L is the tangent to the graph of y= f(x) at the pointx = 3.

I'm equaling both graphs like this:

4x^2 - x^3 = 18 - 3x

and then I isolate everything to the right:

0 = x^3 - 4x^2 - 3x + 18

But I don't know how to factor this...am I in the right track to prove that this line is tangent to the function?

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# Homework Help: Easy tangent line problem but I don't know how to approach it

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