well, without seeing your work, i don't know which step you're going wrong with.

it's usually a matter of arithmetic, and you need to be really careful with your signs.

if i delete the 2nd row, and first column, i get this:

since i+j = 2+1 = 3, this gets multiplied by -1, so we get 5.

along the bottom row, 1st column:

since i+j = 1+1 = 2, this stays as-is.

bottom row, 2nd column:

since i+j = 3+2 = 5, this gets multiplied by -1, so it becomes 1.

bottom row, 3rd column:

since i+j = 3+3 = 6, this stays as-is.

so i get what you say you're "supposed to get".