Discover Questions

Surface by rotating the arc y^2=9x from x=0 to 4 through 2π around x axis is 49π.Show that
x̄ of this surface is: 3/49*integral{x(4x+9)dx}? Why are Ronaldos and Ronaldinios so good at football? How ruler describe me? What is the mass of nitric acid that can be produced from 549g of ammonia? Please include steps so I can learn to do it on my own, thanks!? How do I find the tangent plane to surface?
I need to find the tangent plane at (3,4,-3) for the equation:
x^2+y^2-z^2-4xy+4xz=-68?