Chapter 5 - Polynomials and Factoring - 5.7 Solving Quadratic Equations by Factoring - 5.7 Exercise Set - Page 353: 70

$$ 6.8\times 10^{-4}$$

Recall, for a number to be in scientific notation, it must be in the form $a\times 10^b$, where a must be between 1 and 10. Thus, we simplify the expression. If necessary, we change b until the value of a is between 1 and 10. Doing this, we find that the expression becomes: $$ 6.8\times 10^{-4}$$