Show that 12coshx - 4sinhx = 4e^x + 8e^-x

Using the definitions of coshx and sinhx (coshx=1/2(e^x+e^-x) and sinhx=1/2(e^x-e^-x)), we can substitute these into what we want to show, giving 12(1/2(e^x+e^-x)) - 4(1/2(e^x-e^x)), expanding this out gives 6e^x+6e^-x -2e^x - (-2e^-x), we can collect like terms and it gives 4e^x+8e^-x, as required