Partial derivatives; Tangent Planes

[JC3187]

Hi guys,

Question is:

Find the slopes of the curves of intersection of surface z = f(x,y) with the planes perpendicular to the x-axis and y-axis respectively at the given point.

z = 2x²y ...at (1,1).

f_x(x,y) = 4xy ∴ Slope = 4
f_y(x,y) = 2x² ∴ Slope = 2

Is this wrong?

Answer has it the other way around fx = 2 and fy =4

what mistake did i make?

Thanks

 

[Mark44]

Hi guys,

Question is:

Find the slopes of the curves of intersection of surface z = f(x,y) with the planes perpendicular to the x-axis and y-axis respectively at the given point.

z = 2x²y ...at (1,1).

f_x(x,y) = 4xy ∴ Slope = 4
f_y(x,y) = 2x² ∴ Slope = 2

Is this wrong?

Answer has it the other way around fx = 2 and fy =4

what mistake did i make?

Thanks

Your work looks fine. It looks like they switched the values in the "answer" you showed.

 

[JC3187]

I thought so too, thanks!