1. The problem statement, all variables and given/known data Show that the function is a solution of the wave equation utt = a2uxx. u = (t)/(a2t2-x2) 2. Relevant equations Quotient rule (f/g)' = (g*f ' - f*g') / g2 3. The attempt at a solution I began with the first and second partials of u with respect to x: http://imageshack.com/a/img661/7646/Xnbsd2.png [Broken] I'm fairly confident that this part is correct, because I checked it with an online calculator. Then I did the first partial of u with respect to t: http://imageshack.com/a/img537/4254/5hYVrv.png [Broken] Then the second partial: http://imageshack.com/a/img537/7426/Xr15AC.png [Broken] So I'm getting -utt = a2uxx. I've done this several times now, and I keep getting the extra negative sign in utt. I can't figure out where it's coming from; I'm sure it's some silly mistake with a dropped sign somewhere. I'd appreciate the help of anyone who could help me spot it.