WEBVTT

1
00:00:00.000 --> 00:00:04.005
Here is the problem: x squared/2 to the power x.

2
00:00:04.455 --> 00:00:10.272
Find the limit of x squared/2 to the power x as x → ∞.

3
00:00:11.072 --> 00:00:21.904
Indeterminate form ∞/∞ — apply L prime Hôpital prime s rule. Differentiate the numerator and the denominator separately (this is not the quotient rule).

4
00:00:22.354 --> 00:00:33.314
Indeterminate form ∞/∞ — apply L prime Hôpital prime s rule. Differentiate the numerator and the denominator separately (this is not the quotient rule).

5
00:00:33.764 --> 00:00:42.657
Bounded numerator over an unbounded denominator. The numerator approaches 2 and the denominator grows without bound, so the quotient approaches 0.

6
00:00:43.457 --> 00:00:45.733
So the answer is Limit equals 0.

7
00:00:46.183 --> 00:01:01.566
A limit describes the value a function approaches, not necessarily the value it takes. When substitution gives an indeterminate form, the expression is rewritten (L prime Hôpital prime s rule, a conjugate, or logarithms) until substitution works.

8
00:01:02.366 --> 00:01:26.631
Numerical values as x grows agree: f(127.18281) equals 0, f(1271.8281) equals 0, f(12718.281) equals 0, f(127182.81) equals 0, which checks out.
