Question

X + x^2 + x^3 + x^4 + x^5 +x^6/ x^-1 + x^-2 +x^-3 + x^-4 + x^-5 +x^-6

Answer 1

(x + x² + x³ + x⁴ + x⁵ + x⁶)
a = x
r = x²/x = x
S₆ = a(r^n - 1)/(r - 1)
= x(x^n - 1)/(x - 1)

x⁻¹ + x⁻² + x⁻³ + x⁻⁴ + x⁻⁵ + x⁻⁶
a = x⁻¹
b = x⁻²/x⁻¹ = x⁻¹
S₆ = a(r^n - 1)/(r - 1)
= x⁻¹(x^(-n) - 1)/(x⁻¹ - 1)

maka:
x(x^n - 1)/(x - 1) : x⁻¹(x^(-n) - 1)/(x⁻¹ - 1)
= (x²(x^n - 1)/(x - 1)) * (-(x - 1)/x)/(-(-x^n - 1)/x^n)
= x^(n + 1)

ket: ^ = pangkat

Answer 2