Question 975410: Find f'(x) for f(x)=√(1-8x) using the definition of the derivative Found 2 solutions by stanbon, Edwin McCravy:Answer by stanbon(75887) (Show Source):
You can put this solution on YOUR website! Find f'(x) for f(x)=√(1-8x) using the definition of the derivative
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f'(x) = (1/2)(1-8x)^(-1/2)*(-8)
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= -4/sqrt(1-8x)
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Cheers,
Stan H.
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The other tutor did not use the definition, he just used the formula.
Multiply by
Multiply out numerator (FOIL):
Cancel the h's:
Now we can substitute 0 for h
The bottom terms are like terms:
Cancel the 2 into the 8:
Edwin
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