The numbers 0-9 are lined up in a row, like this:

0 1 2 3 4 5 6 7 8 9

You have to put in + and - signs in the blanks, so that in the end it will all equal 1.

Also, if possible, try to make expressions resulting in 0 and -1.

0+1-2+3+4-5-6+7+8-9=1

0-1+2-3-4+5+6-7-8+9=-1

It is impossible for 0 (because 0+1+2+3+4+5+6+7+8+9=45 that is odd (a-b is odd if a+b is odd and a-b is even if a+b is even so we can get an even number))