# Power Functions Help

• Jul 13th 2010, 04:23 PM
MrOoh
Power Functions Help
Hey I'm having trouble with trying to figure these two problems out:

Let f(x) = cx^3.31. How do the function values f(3.6) and f(5.5) compare?

Let f(x) = cx^4.2 and suppose that f(4) = 18. Find the value of c.

I've tried plugging them all in and subtracting but i can't seem to figure it out
• Jul 13th 2010, 04:36 PM
skeeter
Quote:

Originally Posted by MrOoh
Hey I'm having trouble with trying to figure these two problems out:

Let f(x) = cx^3.31. How do the function values f(3.6) and f(5.5) compare?

Let f(x) = cx^4.2 and suppose that f(4) = 18. Find the value of c.

I've tried plugging them all in and subtracting but i can't seem to figure it out

1. to compare the two values, divide f(5.5) by f(3.6)

2. $\displaystyle 18 = c \cdot 4^{4.2}$ ... solve for c
• Jul 13th 2010, 04:49 PM
MrOoh
Figured out #1

5.3^3.27 / 3.4^3.27

For #2 I get .05 but it's incorrect;

18 = c4^4.2
18 = c337.79
.053 = c
• Jul 13th 2010, 05:03 PM
skeeter
Quote:

Originally Posted by MrOoh
Figured out #1

5.3^3.27 / 3.4^3.27

For #2 I get .05 but it's incorrect;

18 = c4^4.2
18 = c337.79
.053 = c

how do you know it's incorrect?
• Jul 13th 2010, 05:06 PM
MrOoh
Quote:

Originally Posted by skeeter
how do you know it's incorrect?

http://cl.ly/1e2V/content

I plugged it in as you said the first time and I thought i was doing something wrong- The webApp is WebAssign; .053 == .05
• Jul 13th 2010, 05:18 PM
skeeter
the value of c is correct.
• Jul 13th 2010, 05:24 PM
MrOoh