# graphing question

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• Nov 18th 2010, 08:01 AM
math321
graphing question
for the longest while i've been working on this question
can any 1 help me out here

Code:

``` f(x) = 3^(x + 1) and g(x) = 3-x + 3 . Find the point of intersection of the graphs of f and g by solving f(x) = g(x).```
• Nov 18th 2010, 09:07 AM
Unknown008
$3^{x+1} = 3-x+3$

Is that it? g(x) seems strange...
• Nov 18th 2010, 09:14 AM
math321
sorry this is what the question said
Code:

`3^{x+1} = 3^{-x+3}`
• Nov 18th 2010, 09:16 AM
Unknown008
$3^{x+1} = 3^{3-x}$

Insert log on both sides:

$\log 3^{x+1} = \log 3^{3-x}$

$(x+1)\log 3 = (3-x)\log 3$

$(x+1) = (3-x)$

Can you finish now? (Smile)
• Nov 18th 2010, 09:21 AM
math321
so am i solving for x

then what
• Nov 18th 2010, 09:22 AM
Unknown008
You don't need to use quadratic... (Wondering)
• Nov 18th 2010, 09:25 AM
math321
so how am i going to get the points
• Nov 18th 2010, 09:26 AM
Unknown008
You solve for x...

$x+1 = 3-x$
• Nov 18th 2010, 09:29 AM
math321
3-x -x -1=0

-2x +2 = 0
x = -1

is it this
what do i do after
• Nov 18th 2010, 09:31 AM
Unknown008
Since you are looking for the point of intersection, you are looking for a coordinate.

You already have the x coordinate, what can you do it this and the two equations:

$f(x) =3^{x+1}$

$g(x) = 3^{x-3}$
• Nov 18th 2010, 09:34 AM
math321
so i solved the equation above and got -1
so am i going to substitute it in fx and gx
and solve
• Nov 18th 2010, 09:40 AM
Unknown008
Yes (Smile)

Substituting in either f(x) or g(x) should be enough though.
• Nov 18th 2010, 09:52 AM
math321
i guess i have to substitute for both

bcuz they said for f and g

for f i got (-1,1)
any suggestions
• Nov 18th 2010, 09:59 AM
Unknown008
Well... actually you didn't solve for x properly... I thought that you were doing the calculations well, but a small mistake crept in:

-2x +2 = 0

-2x = -2
x = 1

• Nov 18th 2010, 10:27 AM
math321
cud u jus verify this for me
0 = 3-1-2x
0 = 2-2x
-2= -2x
x=1

f(x) = 3^(x+1)

f(x) = 3^ (1+1)
f(x)= 9

g(x) = 3^(-1+3)

g(x) = 3^(2)
g(x) = 9
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