What is the sum of the series?

Question

4

∑ (2k+7)

k=1

 

(the 4 is suppose to be right on top od the symbol)

 

 

 

_______________________

Answer 1

(2(1) + 7 ) + (2(2) + 7) + (2(3) + 7 ) + (2(4) + 7)

2 + 7 + 4 + 7 + 6 + 7 + 8 + 7

48

 

The formula is 

 

S_n = (n/2)(2a₁ + (n - 1)d), where S = the sum, n = number of terms, a₁ = first term, d= common difference.

 

S₄ = (4/2)[2(9) + (4 - 1)2]

S₄ = 2[18 + 6]

S₄ = 2(24)

S₄ = 48