M michi New member Joined Jan 10, 2006 Messages 5 Jan 30, 2006 #1 I can't seem to wrap my head around this function integral [(x^3)/sqrt(x^2+1)] dx The answer is 1/3 sqrt(x^2 +1) * (x^2-2) +C I don't know how they got that answer. Help is greatly appreciated.
I can't seem to wrap my head around this function integral [(x^3)/sqrt(x^2+1)] dx The answer is 1/3 sqrt(x^2 +1) * (x^2-2) +C I don't know how they got that answer. Help is greatly appreciated.
tkhunny Moderator Staff member Joined Apr 12, 2005 Messages 11,325 Jan 30, 2006 #2 Try both of these and see which you like better: u = x^2 + 1 ==> x^2 = u - 1 or u^2 = x^2 + 1 ==> x^2 = u^2 - 1
Try both of these and see which you like better: u = x^2 + 1 ==> x^2 = u - 1 or u^2 = x^2 + 1 ==> x^2 = u^2 - 1
