The Casio calculator distinguishes, using different keys, between the unary operation of negation and the binary operation of subtraction.
To enter a negative number, use the negation key, ( - ), located to the left of the EXE key. To subtract two numbers, use the minus located above the EXE key.
For example, to subtract -5 from 17, compute 17 - (-5). Press MENU 1 to access the RUN-MAT menu. Press
1 7 - ( ( - ) 5 ) EXE
To enter the function Y1 = -X, use the negation key, not the minus sign.