Answer:
P = (2, 3)
Step-by-step explanation:
P is a local minimum, so can be found from the upper zero of the derivative.
y' = 0 = 3x^2 -8x +4
0 = (3x -2)(x -2)
x = 2/3, x = 2
So, the x-coordinate of P is 2. The y-coordinate is found by evaluating the function:
y = ((x -4)x +4)x +3 = ((2 -4)2 +4)2 +3 = 3
The coordinates of P are (2, 3).
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A graphing calculator confirms this result.
By first principles, the derivative is
Use the binomial theorem to expand the numerator:
where
The first term is eliminated, and the limit is
A power of in every term of the numerator cancels with
in the denominator:
Finally, each term containing approaches 0 as
, and the derivative is