CODEWITHSUNDEEP
wolfram-mathematica
Samuel Song
Samuel Song

Reputation: 2185

How to show summation function in Mathematica Instead of expand the whole series?

I am trying to compute the derivative for my homework assignment, and the homework is using a Summation series where i have shown in the first line of my code.

Mathematica expanded all terms for me in this series. I am wondering if there is a way i can make it return the result using an Epsilon sign.

f[x_]=Sum[k*Exp[-Subscript[a,k]*x^3],{k,1,7}]

E^(-x^3 Subscript[a, 1]) + 2 E^(-x^3 Subscript[a, 2]) + 
 3 E^(-x^3 Subscript[a, 3]) + 4 E^(-x^3 Subscript[a, 4]) + 
 5 E^(-x^3 Subscript[a, 5]) + 6 E^(-x^3 Subscript[a, 6]) + 
 7 E^(-x^3 Subscript[a, 7])

f'[x]

-3 E^(-x^3 Subscript[a, 1]) x^2 Subscript[a, 1] - 
 6 E^(-x^3 Subscript[a, 2]) x^2 Subscript[a, 2] - 
 9 E^(-x^3 Subscript[a, 3]) x^2 Subscript[a, 3] - 
 12 E^(-x^3 Subscript[a, 4]) x^2 Subscript[a, 4] - 
 15 E^(-x^3 Subscript[a, 5]) x^2 Subscript[a, 5] - 
 18 E^(-x^3 Subscript[a, 6]) x^2 Subscript[a, 6] - 
 21 E^(-x^3 Subscript[a, 7]) x^2 Subscript[a, 7]

Many thanks!

Upvotes: 1

Views: 2895

Answers (1)

Chris Degnen
Chris Degnen

Reputation: 8655

Use HoldForm to display the sum:-

HoldForm[Sum[k*Exp[-Subscript[a, k]*x^3], {k, 1, 7}]]

You can use E instead of Exp to display output as e. TraditionalForm may further improve the appearance:-

HoldForm[Sum[k*E^(-Subscript[a, k]*x^3), {k, 1, 7}]] // TraditionalForm

enter image description here

Upvotes: 2

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