If y=e^{-x^{2}}, what are the points of inflection, concavity and

Ricardo Berger

Ricardo Berger

Answered question

2022-04-22

If y=ex2, what are the points of inflection, concavity and critical points?

Answer & Explanation

eslasadanv3

eslasadanv3

Beginner2022-04-23Added 20 answers

Step 1
Given: f(x)=ex2
we can calculate the first and second order derivatives:
f(x)=2xex2
fx)=2ex2+4x2ex2=2(2x21)ex2
we can therefore determine that:
(1) By solving the equation:
f(x)=02xex2=0
we can see that f(x) has a single critical point for x=0, this point is a relative maximum since f0)=2<0
Looking at the second derivative, we can see that 2ex2 is always positive and non null, so that inflection points and concavity are determined by the factor (2x21).
Step 2
(2) f(x) has two inflection points for:
2x21=0x=±12
Step 3
(3) As (2x21) is a second order polynomial with leading positive coefficient, we know that is is negative in the inteval between the roots, and positive outside, so:
f(x) is concave up in (,12) and in (12,+)
f(x) is concave down in (12,12)

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