1. f(x) =4

(√5 - x)

Note: 5 - x is all squared.

2. f(x) =2x

x - 2

3. f(x) =√x + 2

3

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- Oct 2nd 2009, 01:29 PMvaleriegriffUse the definition of Derivative to find f`(x)
**1. f(x) =**__4__

**(√5 - x)**

Note: 5 - x is all squared.

2. f(x) =__2x__

x - 2

3. f(x) =__√x + 2__

3 - Oct 2nd 2009, 02:08 PMHallsofIvy
Is it all

**squared**or all in the square root? A clearer way of writing that would be 4/√(5- x). Use parentheses!

That is equal to $\displaystyle 4(5- x)^{-1/2}$. Use the "power rule" (derivative of $\displaystyle x^n$ is $\displaystyle n x^{n-1}$ and the chain rule.

Quote:

[SIZE=5]

2. f(x) =__2x__

x - 2

Quote:

**3. f(x) =**__√x + 2__

3

Again, "power rule" and "chain rule". - Oct 8th 2009, 04:04 PMvaleriegriff
i understand the concept of rules. but the problem i am having with these questions is that i was asked to find the derivative using the definition. i know the definition is

f`(x) = f( x + h) - f(x) Żall over- h

but when i place the equations into the definition i cannot get the same answer as the rules. there is something i am doing wrong and i dont know what..

please help.. - Oct 8th 2009, 04:09 PMmr fantastic