You can put this solution on YOUR website! Find the slope over the interval [0,4]
Y=(X^3)-2x
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f(x) = x^3 - 2x
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f(4) = 64 - 8 = 56
f(0) = 0
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(56 - 0)/4 = 14, the slope of the line between the 2 points.
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The slope at any point is 3x^2 - 2