I'm trying to figure out this equation. [tex] {\Psi} = Ae^{-a(bx-ct)^2} [/tex] I've expanded this to [tex] {\Psi} = Ae^{-ab^2x^2-abxct-ac^2t^2} [/tex] When I try to find the derivative I get this [tex] \left(\newcommand {\pd}[3]{ \frac{ \partial^{#3}{#1} }{ \partial {#2}^{#3} } } \pd{\Psi}{t}{}\right)_x = (-2ac^2t-abxc)Ae^{-ab^2x^2-abxct-ac^2t^2} [/tex] I should get this instead [tex] \left(\newcommand {\pd}[3]{ \frac{ \partial^{#3}{#1} }{ \partial {#2}^{#3} } } \pd{\Psi}{t}{}\right)_x = (-2abcx-2ac^2t)Ae^{-ab^2x^2-abxct-ac^2t^2} [/tex] Can anyone tell me where my error is and how I can fix it?