Free points everyone

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Me answer number 3plz explain how you do it

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

The difference of two numbers is 40. find the numbers if 0.3 parts of one number is equal to 37.5% of the other one.