The calculator has two minus signs
- The regular MINUS sign which is used with the subtraction operation. This operation is binary, requiring two operands (two terms). In a-b, a and be are the operands (they very specific names, but I will skip this detail).
- The negation or change sign. This operation is called unary, requiring one operand. -a means take the negative of the number a.
These are the technicalities, in which you may not be interested. On calculators, the two operations are implemented differently, with two signs, the regular minus sign -- , and the change sign (-) usually smaller in size than the regular -- sign and raised above the main line.Examples
. Let (-) be the negation and -- the regular minus.
- If you enter (-) 12 the TI84Plus accepts it and calculates the negative of 12.
- If you enter 12 (-) 13 the TI protests with a syntax error
- If you enter 12 ( (-) 13) the calculator interprets it as 12* (-13) and calculates -156.
- If you enter --12, the calculator displays Ans--12, where Ans is the last result calculated. If Ans happens to be 0, the new result is obviously the one you are expecting. But if Ans holds a non zero value, this is incorrect.
Suppose you have to calculate X^(-2)*X^(-1/3)
You can enter it exactly as it is written above. In this case, you must use the change sign (-) in both factors.
You can also decide to use the power rules and enter the expression as X^( -2 --1/3). In this case the first minus is the negation and the second is the regular minus.
I could go on with a few more examples, but that will take us away from your present concern.
- If the minus sign is the leftmost (first) symbol in your function (after the Y1=) you should use the negation. Any subsequent minus should be the regular minus --
- If the minus sign is the first symbol in an exponent, you must use the negation. Any subsequent minus in the expression of an exponent should be the regular minus --
I hope it did not bore you death with details you do not care to know about. I do hope that it will help you prevent this type of syntax errors.
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