Derivatives of Quadratic Polynomials
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Given:f(x) = -3x2 + 8x + 2
Problem:Determine the derivative of f(x) using the definition of a derivative.

f ' (x) = lim
f(x+h) - f(x)
h
h→0

f ' (x) = lim
-3(x+h)2+(x+h)+2 - (-3x2+8x+2)
h
h→0

f ' (x) = lim
-3(x2+xh+h2)+8(x+h)+2 - (-3x2+8x+2)
h
h→0

f ' (x) = lim
-3x2+xh-3h2+8x+8h+2 + x2-8x-2
h
h→0

f ' (x) = lim
xh+h2+h
h
h→0

f ' (x) = lim
h(x+h+)
h
h→0

f ' (x) = limx+h+
h→0

f ' (x) =  x+