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January 25, 2015

January 25, 2015

Posted by **Anonymous** on Wednesday, March 13, 2013 at 9:12pm.

If x3 + y3 - xy2 = 5, find dy/dx.

(b)

Using your answer to part (a), make a table of approximate y-values of points on the curve near x = 1, y = 2. Include x = 0.96, 0.98, 1, 1.02, 1.04.

(c)

Find the y-value for x = 0.96 by substituting x = 0.96 in the original equation and solving for y using a computer or calculator. Compare with your answer in part (b).

(d)

Find all points where the tangent line is horizontal or vertical.

- calculus -
**Reiny**, Wednesday, March 13, 2013 at 9:26pma) Assuming you meant

x^3 + y^3 - x y^2 = 5

3x^2 + 3y^2 dy/dx - x(2y)dy/dx - y^2 = 0

dy/dx(3y^2 - 2xy) = y^2 - 3x^2

dy/dx = (y^2 - 3x^2)/(3y^2 - 2xy)

b) just arithmetic, you do it

c) yours

d) for a horizontal tangent, dy/dx = 0

then y^2 - 3x^2 = 0

y^2 = 3x^2

y = ± x√3

sub into the first:

x^3 + 3√3x^3 - x(x√3) = 5

x^3 + 3√3 x^3 - √3 x^2 - 5 = 0

Nastiness!!!!

wolfram says x = 1.03412 correct to 5 decimals

now sub that into the original and find y, equally nasty.

for vertical asymptote , denominator of dy/dx = 0

3y^2 - 2xy) = 0

y(3y - 2x) = 0

y = 0 , that is not bad

or

y = 2x/3

more mess ahead

I suggest you use the Wolfram page or your built-in equation solver of your fancy calculator to solve these equations.

(it might be a good idea to check my work, lately I have been making silly errors by not writing out the solution first)

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