Question

The maximum value of f(x) = -e^x + x is:

Answer 1

A) 0
B) 2
C) ln 2
D) -1
E) 1

Answer 2

Diff it and put equal to 0

Answer 3

ok

Answer 4

f'(x) = -e^x

Answer 5

What about the other bit?

Answer 6

+ 1

Answer 7

f'(x) = -e^x + 1

Answer 8

So put it equal to O

Answer 9

0 = -e^x + 1

Answer 10

x=?

Answer 11

the e is euler's constant right?

Answer 12

Euler's constant is something else, sometimes it's called Euler's number

Answer 13

Anyway, u got your answer, right?

Answer 14

nope. can you take it from here?

Answer 15

e is the number 2.7... etc.
Subtract 1 from the above equation, you will get:
-1 = -e^x => e^x = 1
Take the natural log on both sides:
x = ln(1) = 0 :-)

Answer 16

So now sub that in your original to get the max value.

Answer 17

-1 yay! thanks you guys.