How would the imaginary number 7/2i be written as a complex number?

Proceed as in example 3 in section 6.1 to rewrite the given expression using a single power series whose general term involves xk. ∞ n(n − 1)cnxn − 2 n = 2 − 4 ∞ ncnxn n = 1 + ∞ cnxn n = 0

Find the value. a. 0.003 b. 0.03 c. 0.3 d. 3

[10 points, algebra 2]according to my answer key the restrictions are -1 and 4. but why not positive 1?