Question 903582
f(x)=4-x^2; x=9, x=9+h
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f(9+h) = 4 - (9+h)^2 = 4 -81 -18h -h^2
f(9) = 4- (81) = -77
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Rate of change at x = 9 is [f(9+h)-f(9)]/h
rate of change at x = 9 is [-18h-h^2]/h = -18 -h
Note:: As h goes to zero, rate goes to -18 
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Cheers,
Stan H.