precal question

Question

Write the sum without using sigma notation.

n	(−1)j + 4 xj
j = 1

 

+

+

+

···

+

a1

a2

a3

an

Answer 1

(-1)^j+4

(-1)^j(-1)⁴

(-1)^j(1)

(-1)^j

a_n = (-1)ⁿxⁿ

a₁ = -x

r = -x

S_n = [a₁(1 - rⁿ)] / (1 - r)

S_n = [-x(1 - (-x)ⁿ] / (1 + x)