2) (a - b)(a+b)≠(a^2 - b^2). Algebraically equal expressions are not equal to a computer.

3) Addition is not commutative.

The order of addition can drastically affect the answer!

4) A computer can not subtract or multiply without possible disastrous error.

5) You never use the quadratic formula to solve a quadratic equation because on a computer it might give inaccurate results.

6) Newton's iteration though taught is rarely the best one for the job.

7) A computer can not always compare theoretically equal quantities.

8) There is a largest number to a computer.

9) A computer can have three states for a matrix, singular, non singular and nearly singular!

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