What is the surface area of the solid created by revolving f(x) = 2x^2-4x+8 , x in [1,2]f(x)=2x24x+8,x[1,2] around the x axis?

1 Answer
May 29, 2016

approximately 100.896100.896

Explanation:

The surface area SS created by revolving the function f(x)f(x) around the xx-axis on the interval x in[a,b]x[a,b] can be found through:

S=2piint_a^bf(x)sqrt(1+[f'(x)]^2)dx

Using f(x)=2x^2-4x+8 and f'(x)=4x-4 on the interval x in[1,2] gives:

S=2piint_1^2(2x^2-4x+8)sqrt(1+(4x-4)^2)dx

Actually integrating this is very complex and far beyond the scope of this problem, so put this into a calculator--be mindful of parentheses.

The answer you receive (don't forget to multiply by 2pi) should be

Sapprox100.896