In the book R. M. Young: An introduction to non-harmonic Fourier series, I came across the following problem (page 18):

Problem. Show that the sequence $\left \{ \frac{1}{x+1},\frac{1}{x+2},\frac{1}{x+3}, \dots \right \}$ is complete in $L^2[0,1]$.

I tried to apply the Müntz-Szász theorem but it didn't work out. Any ideas or approaches how to show completeness here? Thanks!