Wednesday, October 17, 2007

Today's Slides: October 17

Here they are ...



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9 comments:

«Craig» said...

I got it! very good question it made me think fairly hard about it.
However, I don't think that everyone has had sufficient time to look at it, so I won't post my answer until after me Scribe post, which will be a little bit later tonight =)

October 17, 2007 at 5:59 p.m.
m@rk said...

WOW, I seriously just don't get this question. The only thing that i know is that c is the slope because it is the derivative. Other than that the last question seems to make no sense to me.So my answer will be:

f(x)=cx+b

I don't know if that makes sense. Now back to some serious studying for our pretest.

October 17, 2007 at 7:05 p.m.
aichelle s. said...

hmm well after some thinking I think that it's:

f(x) = cx + (b-a)

However, I don't know if I am correct. It worked for the previous questions that we did in class.
I honestly don't know how to explain how I got that but c is the slope. The only reason why I had b - a is because I was trying to figure out what I could get to get f(x). I don't know how to explain why it works.

October 17, 2007 at 8:05 p.m.
m@rk said...

I was thinking of that same function at first but i just couldnt explain the (b-a) part, thats why i just sticked with my guts. This question is tough. I think i'm just gonna ask my sister when she gets home.

October 17, 2007 at 9:01 p.m.
«Craig» said...

Well, here goes...

Now, I'm looking at the other possible answers and wondering if mine might be wrong, but I got:

f(x) = cx + (b-ac)

Now, my explanation?..

Well to find the equation of a line all that is needed is the slope and the y-intercept. Now we are already given the slope (f'(x)=c). Now all we need is the intercept. Well we know one point (a,b) so to find the intercept:
-first, find the distance from the point(a,b) to (0,b). Obviously it's a.
-next, since the slope is the change in y over the change in x, and you already know the change in x and the slope, you can use:

slope = ∂y / ∂x
c = ∂y / a
∂y = c • a

-So now the y coordinate of the y-intercept is the y coordinate(b) subtract ∂y. (b - ca)
-Now that we have the slope and y-intercept, plug it into the equation of a line to get:

f(x) = m • x + y-int.
f(x) = c • x + (b - c • a)
or
f(x) = cx + (b-ac)

WOW, that could have been a scribe post in itself LOL... Oh well, I hope everyone understands =)

October 17, 2007 at 9:26 p.m.
«Craig» said...

BTW Aichelle, you were so close, you just forgot to multiply a by c because you only used the previous questions as examples (all slopes of 1 so c=1) You had it!

October 17, 2007 at 9:27 p.m.
aichelle s. said...

haha oh! nice thanks for explaining it you're so smart Craig!

October 17, 2007 at 9:41 p.m.
m@rk said...

wow! I got it now but i have a different explanation.

If f(x) = c then the f(x) = cx + m, where m is some constant. We also know that f(a) = b which means
f(a) = ca + m = b solve this for m to get
m = b - ca. Put this into the equation for f(x) and you get

f(x) = cx + b - ca

(All the credits belong to the person who helped me on yahoo answers)

October 17, 2007 at 10:01 p.m.
Tim_MATH_y said...

After looking at all the collective comments, I find that I totally agree with your answer, Craig and Mark.

Craig's definition was more in depth it seems yet hard to follow. However, I loved the explanation you came up with MArk!

However, good job to you all for your efforts =)

October 18, 2007 at 7:40 p.m.

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