# another question about functions (last question today, I promise)

• Oct 17th 2009, 11:17 AM
md56
another question about functions (last question today, I promise)
f(x)=1-4x+6x^2

Calculate following values:
f(a)=
f(a+h)=

Then simplify
f(a+h)-f(a)
_________(over)
h

I feel like this is just a rudimentary substitution problem, but my calculations are all incorrect
• Oct 17th 2009, 11:21 AM
skeeter
Quote:

Originally Posted by md56
f(x)=1-4x+6x^2

Calculate following values:
f(a)=
f(a+h)=

Then simplify
f(a+h)-f(a)
_________(over)
h

I feel like this is just a rudimentary substitution problem, but my calculations are all incorrect

this is a lot of meticulous, grunt work algebra ... I'm lazy today, so hope someone else wants to type it all out.

buena suerte!
• Oct 17th 2009, 11:32 AM
md56
I know, I am constantly assigned problems in which I could fill an entire page with numbers and variables just to find a simple two or three digit answer.
It diminishes my soul power.

Also, did you know that 1 reply to a thread is enough to keep others clear from the bother of opening a thread? Now my thread has 2 replies, and I'll never get an answer!
So thanks for that skeet! (Punch)
• Oct 17th 2009, 03:27 PM
mr fantastic
Quote:

Originally Posted by md56
I know, I am constantly assigned problems in which I could fill an entire page with numbers and variables just to find a simple two or three digit answer.
It diminishes my soul power.

Also, did you know that 1 reply to a thread is enough to keep others clear from the bother of opening a thread? Now my thread has 2 replies, and I'll never get an answer!
So thanks for that skeet! (Punch)

What skeeter said, in a nice way, is the following:

There is a difference between not being able to do a problem because you're stuck and not being able to do a problem because it involves a lot of spade work and you don't want to get dirty. MHF is not here to save people from getting dirty.

So do the spade work. Post what you can do and make it clear where you get stuck.

(Now you have 3 replies. Rather than keeping others clear from the bother of opening this thread, the opposite will probably occur because 3 replies makes it look interesting.)
• Oct 17th 2009, 05:15 PM
md56
What would f(a) equal to, and also what would f(a+h) be equal to. Once I figure out what I need to substitute, I can finish the job.
• Oct 17th 2009, 05:25 PM
mr fantastic
Quote:

Originally Posted by md56
What would f(a) equal to, and also what would f(a+h) be equal to. Once I figure out what I need to substitute, I can finish the job.

$f(a) = 1 - 4a + 6a^2$.

$f(a + h) = 1 - 4(a + h) + 6(a + h)^2 = .....$
where you need to expand and simplify.
• Oct 17th 2009, 07:16 PM
pickslides
Quote:

Originally Posted by md56

I feel like this is just a rudimentary substitution problem,

Yep it is, part 3 requires the hard work from the first two parts (Thanks Mr F) combined with some factoring to cancel out h.