Partial Derivatives

shivers20

Junior Member
Joined
Mar 3, 2006
Messages
68
Let f(x,y)= x^2y^3-x+y^2-50

1. Find fy: (3x^4)(y^2) -0 + 2y - 0 = (3x^4)(y^2)+2y
Do I add the remaining power of y to x?

2. Find f yx i.e (fy)x: What exactly does this represent? Do I take fy of the previous example, when we solved for fx? The answer would be 6x^4y+2

3. Find the slope of the tangent line to the curve of intersection of the graph of f(x,y) and the plane x=3 at the point where x=3 and y=2. I start by plugging in (3,2) into fx= (3x^4)(y^2)+2y which gives me (3(3)^4) (2^2)+2(2)= 328 which leads me to believe I made an error in finding fx.

4. Find a vector parallel to the tangent line in #3
1i+0j+328k

5. Find the parametric equations of the tangent line in #3
x-3=1t
y-2=0t
z-0=328t
 
Lets try this again.

x^2y^3-x+y^2-50

1.fy= 3x^2y^2 +2y

2. (fy)x = 6xy^2

3. Slope= plug in (3,2) into (fy)x or fy? 6(3)(2^2)= 72

4. Vector parallel= 1i+0j+72k

5. Parametric equation= x-3= 1t, y-2=0t, z-0=72t
 
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