Thu gọn S = x^1 x^2 x^3 x^n
Giải thích
Lời giải:
S = x0 + x1 + x2 + x3 + … + xn
xS = x + x2 + x3 + … + xn+1
xS – S = (x + x2 + x3 + … + xn+1) – (x0 + x1 + x2 + x3 + … + xn)
S(x – 1) = xn+1 – x0
S(x – 1) = xn+1 – 1
\(S = \frac{{{x^{n + 1}} - 1}}{{x - 1}}\)