Expression 5: Start sum from "k" equals 0 to infinity , end sum, left parenthesis, negative 1 , right parenthesis Superscript, "k" , Baseline StartFraction, "x" Superscript, 2 "k" plus 1 , Baseline Over left parenthesis, 2 "k" plus 1 , right parenthesis ! , EndFraction∞∑k=0−1kx2k+12k+1!