My daughter is learning scientific notation in school, and her textbook says something to the effect of this:
Scientific notation is a method of writing numbers as the product of two factors where the first factor is a number greater than or equal to 1 but less than 10 and the second factor is a power of 10.
The teacher is taking this to mean that you cannot express a negative number in scientific notation. So that e.g.
$-4 * 10^{50}$
would not be valid scientific notation because -4 is less than 1.
Is there such a view of scientific notation? It certainly doesn't jive with my memory (or wikipedia), or is that description just deficient, and should better read:
Scientific notation is a method of writing numbers as the product of two factors where the first factor is a number whose absolute value is greater than or equal to 1 but less than 10 and the second factor is a power of 10.
And if it is a legitimate view, how do you express negative numbers in scientific notation?