SOLUTION: Find the equation of the tangent to the curve x^2y-x=y^3-8 at x=0.

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Question 1153034: Find the equation of the tangent to the curve x^2y-x=y^3-8 at x=0.
Found 2 solutions by Alan3354, Edwin McCravy:
Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
Find the equation of the tangent to the curve x^2y-x=y^3-8 at x=0.
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I did this, but lost it before it was posted.
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@ x = 0, y = 2
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Differentiate implicitly and find the slope.
Slope = -1/12
---> y = (-x/12) + 2
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email via the TY note if you need help.

Answer by Edwin McCravy(20060) About Me  (Show Source):
You can put this solution on YOUR website!
x^2y-x=y^3-8 at x=0
Substituting x=0,
x%5E2y-x=y%5E3-8
0%5E2y-0=y%5E3-8
0=y%5E3-8
8=y%5E3
2=y

So the point of tangency is (0,2), and we want the equation of the
green line below:



We find the slope of the tangent line, which is the
same as the derivative at that point:  So we find
the derivative implicitly, i.e., without solving for
the independent variable y:

x%5E2y-x=y%5E3-8
x%5E2%2Aexpr%28dx%2Fdy%29%2B2xy-1=3%2Ay%5E2%2Aexpr%28dy%2Fdx%29

We substitute x=0 and y=2 and solve for %22dy%22%2F%22dx%22

0%5E2%2Aexpr%28dx%2Fdy%29-2%280%29%282%29-1=3%2A2%5E2%2Aexpr%28dy%2Fdx%29

0-0-1=3%2A4%2Aexpr%28dy%2Fdx%29

-1=12%2Aexpr%28dy%2Fdx%29

-1%2F12=expr%28dy%2Fdx%29

That's the slope of the tangent line at (0,2), which is
the green line. So

m=-1%2F12

Since the point of tangency is the y-intercept (0,2), we can just
use:

y=mx%2Bb

with 
matrix%281%2C3%2Cm=-1%2F12%2C%22%22%2C+b=2%29

y=expr%28-1%2F12%29x%2B2

Edwin