Average rate of change, functions

elizabethj

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Jan 29, 2013
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9
Here is the problem

A function is given. Determine the average rate of change of the function between the given values of the variable.

g(x)=9+1/2x; x=1, x=5

That is g(x)=9+one half times x


My thought is to plug each x value in and solve which would give me two points (x,y). Using those to points I would then find the slope, which would be the average rate of change of the function between the two variables.

Can someone tell me if that is how you solve this problem?
 
Here is the problem

A function is given. Determine the average rate of change of the function between the given values of the variable.

g(x)=9+1/2x; x=1, x=5

That is g(x)=9+one half times x


My thought is to plug each x value in and solve which would give me two points (x,y). Using those to points I would then find the slope, which would be the average rate of change of the function between the two variables.

Can someone tell me if that is how you solve this problem?

You are correct.
 
After I posted the question I tried to solve it that way and got

for x=1 g(1)=9+1/2(1) (1,19/2)

for x=5 g(5)=9+1/2(5) (5,21/2)

then used those to points to find a slope of -1/4

When I submitted this answer my math program is saying it is incorrect.

My notes on Average rate of change are..

f(x)=x2 -2 x=1, x=2

which would be solved as
f(2)-f(1)
divided by (or all over)
0-(-2)

Which ends up being three.

I'm very confused on this subject, I'm not sure where I am going wrong or how to apply my notes to the given problem. And this is the simplest rate of change problem I was given!
 
I must have messed up my addition or subtraction or something. I used the method I posted again and got 1/2 as my rate of change, which is apparently right!
 
After I posted the question I tried to solve it that way and got

for x=1 g(1)=9+1/2(1) (1,19/2)

for x=5 g(5)=9+1/2(5) (5,21/2)

then used those to points to find a slope of -1/4

When I submitted this answer my math program is saying it is incorrect.

My notes on Average rate of change are..

f(x)=x2 -2 x=1, x=2

which would be solved as
f(2)-f(1)
divided by (or all over)
0-(-2)
f(2)= 4- 2= 2 and f(1)= 1- 2= -1 so f(2)- f(1)= 2- (-1)= 3.
The denominator is 2- 1= 1, NOT 0- (2).

Which ends up being three.

I'm very confused on this subject, I'm not sure where I am going wrong or how to apply my notes to the given problem. And this is the simplest rate of change problem I was given!
 
here is the problem

a function is given. Determine the average rate of change of the function between the given values of the variable.

G(x) = 9 + (1/2)x; x=1, x=5

elizabethj & lookagain edit said:
after i posted the question i tried to solve it that way and got

for x = 1, g(1) = 9 + (1/2)(1) = 19/2 ---> (1, 19/2) . . . correct

for x = 5, g(5) = 9 + (1/2)(5) = 23/2 ---> (5, > > > 21/2 < < < ) . . . Here is where you made your accident in arithmetic. It should be 9 + (1/2)(5) = 18/2 + 5/2 = 23/2 ---> (5, 23/2).

then used those to points to find a slope of -1/4 . . . Then rework it to get a slope of 1/2.

when i submitted this answer my math program is saying it is incorrect.


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Last edited:
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