The most common mistake made when using the Formula is to accidentally mismatch the x-values and y-values. Be careful you don't subtract an x from a y, or vice versa; make sure you've paired the numbers properly.
Also, don't get careless with the square-root symbol. If you get in the habit of omitting the square root and then "remembering" to put it back in when you check your answers in the back of the book, then you'll forget the square root on the test, and you'll miss easy points.
You also don't want to be careless with the squaring inside the Formula. Remember that you simplify inside the parentheses before you square, not after (due to the Order of Operations), and remember that the square is on everything inside the parentheses, including the minus sign (if your subtraction results in a negative number); the square of a negative is always a positive.
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Answer:
The most common mistake made when using the Formula is to accidentally mismatch the x-values and y-values. Be careful you don't subtract an x from a y, or vice versa; make sure you've paired the numbers properly.
Also, don't get careless with the square-root symbol. If you get in the habit of omitting the square root and then "remembering" to put it back in when you check your answers in the back of the book, then you'll forget the square root on the test, and you'll miss easy points.
You also don't want to be careless with the squaring inside the Formula. Remember that you simplify inside the parentheses before you square, not after (due to the Order of Operations), and remember that the square is on everything inside the parentheses, including the minus sign (if your subtraction results in a negative number); the square of a negative is always a positive.