When multiplying and dividing two numbers in scientific notation, why do u sometimes have to rewrite one factor ?

You sometimes need to rewrite a factor because the lead number is not between 1 and 10 as it needs to be in scientific notation. For instance, if we had lead numbers of 2 and 5, as we do in the following problem.

2x10^3 * 5x10^9

Then we get the answer of 10x10^12. We need to adjust this by moving the decimal place and increasing the exponent by 1. The correct answer would be 1x10^13 instead.

last option

step-by-step explanation:

given that δdef is right and isoceles,

assuming that side df is the hypotenuse means that de an ef are the other 2 sides that intersect at 90° and are of equal length.

because they are of equal length, we can say that they are congruent

because they intersect at 90°, their slopes must be opposite reciprocals.

only the last option satisfies these conditions.