Which number is not in scientific notation? 11 ⋅ 1021 5.7 ⋅ 109 3.1 ⋅ 10−12 1.67 ⋅ 10−5

What is the best way to answer questions with a x expression in the question. for example 3x + 10x=?

Parabolas y=−2x^2 and y=2x^2 +k intersect at points a and b that are in the third and the fourth quadrants respectively. find k if length of the segment ab is 5.

A.s.a.! similarity in right triangles, refer to the figure to complete this proportionc/a = a/? a.) cb.) hc.) rd.) s