# Is my formula for DFT correct?

I'm doing "Digital Image" online course. I tried to solve the following question $x(n_1,n_2)$ is defined as $x(n_1,n_2)=(−1)^{(n_1+n_2)}$ when $0≤n_1$, $n_2≤2$ and zero elsewhere. Denote by $X(k_1,k_2)$, where $0≤k_1$, $k_2≤2$, the DFT of $x(n_1,n_2)$. What is the value of $X(1,2)$?

The answer should be 4, but I get a complex answer. Do I start right or I'm using wrong formula?

• Can someone help please? – theateist Jun 25 '16 at 2:57
• Put your working in TeX form so it is easier to read. – mattos Jun 25 '16 at 4:16