What is the measure of \angle x∠xangle, x?

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

Ineed with math stuff it involves graphs

For a function f(x), a) if f(7) = 22 then f^-1(22) = b) f^-1(f(c)) =