# derivative problem

• Nov 30th 2012, 03:23 AM
salma
derivative problem
1) The derivative of f( x) at x = a can best be described graphically as:
A) Average value of the function, f( x), between x = 0 and x = a.
B) The slope of the line perpendicular to the graph of f (x) and containing the point (a,f(a)).
C) The slope of the line containing the two points (0, f(0) ) and (a, f (a)).
D) The slope of the tangent line to the graph of f (x) at the point (a, f(a) ).

I picked D for this one.

2) If f(x)= 8(sqrt x) + 6x^(3/4), find f '(x).

A) 4x^(1/2) + (9/2)x^1/4

B) 4x^(-1/2) + 8x^-1/4

C) 4(sqrt x) + (18/4)x^1/2

D) 4x^(-1/2) + (9/2)x^-1/4

• Nov 30th 2012, 04:00 AM
BobP
Re: derivative problem
D is correct for (1)

For (2), the rule for differentiating x raised to some power is ' power down to the front, subtract 1 from the power '.

$\displaystyle \sqrt{x} = x^{1/2},$ so ... ?
• Nov 30th 2012, 05:10 AM
salma
Re: derivative problem
Im thinking A?
• Nov 30th 2012, 05:12 AM
salma
Re: derivative problem
No, D
• Nov 30th 2012, 05:38 AM
topsquark
Re: derivative problem
Quote:

Originally Posted by salma
No, D

Yup! (Sun)

-Dan