The coefficient of x5 in 1+2x+3x2+⋯−3/2 is (|x|<1)
21
25
26
0
1+2x+3x2+⋯−3/2=(1−x)−2−3/2=(1−x)3=1−3x+3x2−x3
Therefore, coefficient of x5 is 0.