I need to do a Fourier transform for the next Green's function:$F[(\frac{\mathrm{d} ^{2}}{\mathrm{d} x^{2}}-m^{2})\cdot G(x,x^{'})]$.
My solution is: $\int_{-\infty }^{\infty }(\frac{\mathrm{d} ^{2}}{\mathrm{d} x^{2}}\cdot G(x,x')\cdot e^{-ikx})dx-m^{2}\int_{-\infty }^{\infty }G(x,x')\cdot e^{-ikx}dx=\int_{-\infty }^{\infty }(\frac{\mathrm{d} ^{2}}{\mathrm{d} x^{2}}\cdot G(x,x')\cdot e^{-ikx})dx-m^{2}\widetilde{G}(k)$
but I don't know how to solve the first integral.
The solution is:$-(k^{2}+m^{2})\cdot \widetilde{G}(k)$
Can someone please explain to me how did they get this expression?