Finding the Value of b for a Point of Inflection at (2,0)

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SUMMARY

The problem involves finding the value of b in the cubic function y = x^3 + ax^2 + bx - 8, given that there is a point of inflection at (2,0). The second derivative, y'' = 6x + 2a, is set to zero at x = 2, leading to the conclusion that a = -6. Substituting this value into the first derivative y' = 3x^2 + 2ax + b allows for further analysis. Ultimately, the value of b is determined to be 8.

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Homework Statement


If the graph of y=x^3+ax^2+bx-8 has a point of inflection at (2,0), what is the value of b?
the answer is 8.

Homework Equations





The Attempt at a Solution


y'=3x^2+2ax+b
y''=6x+2a
Let y''=0=6x+2a then i plugged in 2 for x
and got -6=a
So y'=3x^2-12x+b...
I don't know where to go from here.
 
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You get one more equation from the fact that y = 0 at x = 2.
 
i wouldn't of thought of that.
thank you
 

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