Question

Factor completely 21x³ + 35x² + 9x + 15. a.(3x − 5)(7x² − 3) b.(3x − 5)(7x² + 3) c.(3x + 5)(7x² − 3) d.(3x + 5)(7x² + 3)

Answer 1

d

Explanation:

given

21x³ + 35x² + 9x + 15 ( factor the first/second and third/fourth terms )

= 7x² (3x + 5) + 3(3x + 5) ← factor out (3x + 5) from each term

= (3x + 5)(7x² + 3)