Hi All,

I am going through notes our lecturer gave us, am having some problems with it

Given the wave function $\displaystyle \Psi(x,t)=Ae^{-\lambda \mid x \mid} e^{-i\omega t}$ where A, lambda and omega are psoitive real constants and

$\displaystyle \mid x \mid $ either (x greater and equal to 0) and (-x less than or equal to 0)

1) Normalise Psi, 2) Determine the expectation values of x and x^2

I can derive to far as $\displaystyle 1=A^2(\int^{0}_{-\infty} e^{2\lambda x} dx + \int^{\infty}_{0} e^{-2\lambda x} dx)$ Then he changes the integral such that

= $\displaystyle -A^2\int^{0}_{-\infty} e^{-2\lambda x} dx + \int^{\infty}_{0} e^{-2\lambda x} dx = 2A^2\int^{\infty}_{0} e^{-2\lambda x} dx$

Where did the first termof the last expression come out of?

Thanks