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Mathematics 21 Online
OpenStudy (anonymous):

Pre-Calculus question, picture posted. Determining secant equation.

OpenStudy (anonymous):

OpenStudy (anonymous):

The first one. Altho Im not sure what they want in the second one either. I don't really understand what the question is asking of me.

OpenStudy (amistre64):

so, you want to define a line between 2 points ....

OpenStudy (amistre64):

a general point A is defined by f(x)=4^x as 4^A .... right? so we would simply need to define the slope of the line from 4^2 to 4^A, then use the point slope form to define the equation of that line

OpenStudy (anonymous):

so I got f(a)-f(2) divides by a-2

OpenStudy (anonymous):

wouldthat be the equation?

OpenStudy (amistre64):

good, and lets use the point they establish for us as (2,4^2)

OpenStudy (amistre64):

thats not the equation, just the slope of the line between the points

OpenStudy (anonymous):

so I have to integrate something to solve for b?

OpenStudy (amistre64):

\[y=\frac{4^A-4^2}{A-2}(x-2)+4^2\]

OpenStudy (amistre64):

you dont have to integrate anything to find a derivative .... unless thats some method that your marterial has asked you to do

OpenStudy (anonymous):

ohhhh u got the line, figured out thetransformations, and then put them into the equation

OpenStudy (amistre64):

yep ...

OpenStudy (anonymous):

how did u get the transformations

OpenStudy (amistre64):

\[slope=\frac{f(b)-f(a)}{b-a}~:~let f(x)=4^x,~and~b=A~and~a=2\]

OpenStudy (amistre64):

\[slope-point:y=m(x-h)+k~:~text{for some (h,k) point}\]

OpenStudy (amistre64):

the reply isnt formating my coding .. so i cant tell when i mess up :)

OpenStudy (anonymous):

im trying to follow u on paper

OpenStudy (amistre64):

the secant line (a line between 2 points on the same curve) is therefore given to be:\[y=\frac{4^A-4^2}{A-2}(x-2)+4^2\]

OpenStudy (anonymous):

i tried plugging in 2 and 16 and got 16=2m-mh+K

OpenStudy (amistre64):

recall that A is some general value ....

OpenStudy (anonymous):

i still dunno how u gotx-2 or +16

OpenStudy (amistre64):

they give us that information in the setup: use (2,f(2)) to establish your setup

OpenStudy (anonymous):

i know they are trasnformations up and sideways

OpenStudy (anonymous):

man i feel stupid i still dont understand the lastpart:S

OpenStudy (anonymous):

lol sorry

OpenStudy (amistre64):

spose they asked a more basic question, which is really all that this amounts too, as: given a slope 5 and a point (2,1) what is the equation of the line in point-slope format?

OpenStudy (anonymous):

1=10+b b=-9

OpenStudy (anonymous):

y=5x-9

OpenStudy (amistre64):

thats slope-INTERCEPT format ... not point-slope format; even tho it ends up being a correct equation for the line

OpenStudy (amistre64):

when given a slope (m) and a point (h,k); we can construct a line to be defined as: y-k = m(x-h) or written another way: y = m(x-h) + k

OpenStudy (amistre64):

the information in the question supplies is with a slope to determine; and give us a point to use

OpenStudy (amistre64):

\[slope:\frac{4^A-4^2}{A-2}\]\[point:(2,4^2)\]

OpenStudy (anonymous):

ohhhhhhhhhhhhhhhhhhh

OpenStudy (anonymous):

clicked! THANK U

OpenStudy (amistre64):

:) then it asks you how you could use this setup to determine the equation for the slope at a single point

OpenStudy (anonymous):

lol since ur here anyways u know the second question>

OpenStudy (amistre64):

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