How do you solve e^x>30ex>30?

1 Answer
Jul 8, 2018

x > ln(30)x>ln(30)

Explanation:

It may be helpful to look at a graph of e^xex. Notice that because it is an exponential function with a base greater than 1, it is monotonically increasing, so:

e^a > e^b => a > bea>eba>b

To clarify, I'll use a concrete example.

e^2 > e^0 => 2 > 0e2>e02>0

Getting back to our original problem, we want to find when e^xex is greater than 3030. Rewrite 3030 as e^ln(30)eln(30)

e^x > e^ln(30)ex>eln(30)

But if e^x > e^ln(30)ex>eln(30):

x > ln(30)x>ln(30)

Technically, you could also take the natural logarithm on both sides since that is also monotonically increasing.