I am trying to to do a Fourier Transformation with the following started work :
with the question on the paper on the third step, why is the conversion from $$(-1)^n= e^{-j\pi n}$$ when I thought it was $$(-1)^n = (e^{j\pi})^n = e^{j\pi n} $$ Also I am a little confused what to do from the last step. I know the final answer will be $$ X(e^{jw}) = 2\pi \sum_{k=-\infty}^\infty \delta[\omega - (2k+1)\pi] $$ but I'm confused after the last step shown in the image above.