Answer:
∑ₙ₌₀°° (-3x)ⁿ / n!
R = ∞
Explanation:
Maclaurin series is:
∑ₙ₌₀°° f⁽ⁿ⁾(0) xⁿ / n!
Find the nth derivative and evaluate at x=0:
f(x) = e⁻³ˣ
f⁽ⁿ⁾(x) = (-3)ⁿ e⁻³ˣ
f⁽ⁿ⁾(0) = (-3)ⁿ
The Maclaurin series is therefore:
∑ₙ₌₀°° (-3)ⁿ xⁿ / n!
∑ₙ₌₀°° (-3x)ⁿ / n!
Use ratio test to find the radius of convergence.
lim(n→∞)│aₙ₊₁ / aₙ│< 1
lim(n→∞)│[(-3x)ⁿ⁺¹ / (n+1)!] / [(-3x)ⁿ / n!]│< 1
lim(n→∞)│(-3x) n! / (n+1)!│< 1
lim(n→∞)│3x / (n+1)│< 1
0 < 1
The radius of convergence is infinite.