How is the intersection and union in clusters

Write a recursive sequence that represents the sequence defined by the following explicit formula:

Pick the expression that matches this description: a polynomial of the 5th degree with a leading coefficient of 7 and a constant term of 6 (choice a) 7x^5+2x^2+6 (choice b) 7x^6−6x^4+5 (choice c) 6x^7−x^5+5 (choice d) 6x^5+x^4+7

Which inequality comparing two of the expressions is true when 0.7 < x < 0.9