Find the equation of the tangent to the curve defined by y =e^x that is
perpendicular to the line defined by 3x+y=1.
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OpenStudy (kc_kennylau):
There are three pieces of information here:
1. it's a straight line (any tangent must be a straight line)
2. it's tangent to the curve y=e^x
3. it's perpendicular to the line 3x+y=1
OpenStudy (anonymous):
I got y=1/3 e^x but the answer should be
x-3y+(1+ln3)=0
How do I get that answer?
OpenStudy (kc_kennylau):
Let's find the slope of the line from the third piece of information
OpenStudy (anonymous):
m=-3 in the line so slope of perpendicular line should be 1/3
OpenStudy (kc_kennylau):
yep
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OpenStudy (kc_kennylau):
At which point of the curve y=e^x will the slope of the tangent be 1/3?
OpenStudy (anonymous):
um -1?
OpenStudy (kc_kennylau):
Why so?
OpenStudy (anonymous):
ln1/3?
OpenStudy (kc_kennylau):
I'm asking for a point... A point has 2 coordinates...
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OpenStudy (anonymous):
(-1,1)
OpenStudy (kc_kennylau):
where did the ln1/3 go
OpenStudy (kc_kennylau):
this point ain't even on the curve
OpenStudy (anonymous):
lol idk o.o
OpenStudy (kc_kennylau):
At which point of the curve y=e^x will the slope of the tangent be 1/3?
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OpenStudy (kc_kennylau):
ln1/3 is near
OpenStudy (anonymous):
I'm not sure.
OpenStudy (anonymous):
3e?
OpenStudy (kc_kennylau):
nope
OpenStudy (kc_kennylau):
never mind
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OpenStudy (kc_kennylau):
On the curve y=e^x, when x=ln1/3, y=?
OpenStudy (anonymous):
1/3
OpenStudy (kc_kennylau):
now you can answer
OpenStudy (kc_kennylau):
Now you know that the slope of the line is 1/3, and the line passes through the point (ln1/3,1/3)
OpenStudy (kc_kennylau):
And you should be able to find the equation of the line
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OpenStudy (anonymous):
I got x-3y-ln1/3 +1=0
OpenStudy (kc_kennylau):
Mind showing us the steps?
OpenStudy (anonymous):
y=1/3 (x-ln1/3) + 1/3
expanded and multiplied whole thing by 3