jadi: (3+y)⁷ = C (7,0) x (3)⁷ x (y)⁰ + C (7,1) x (3)⁶ x (y)¹ + C (7,2) x (3)⁵ x (y)² + C (7,3) x (3)⁴ x (y)³ + C (7,4) x (3)³ x (y)⁴ +.......... C (7,7) x (3)⁰ x (y)⁷
C (7,4) x (3)³ x (y)⁴ = x 27 x y⁴ =945 y⁴ jadi suku ke lima (3+y)⁷ adalah ---> 945 y⁴
jadi:
(3+y)⁷
= C (7,0) x (3)⁷ x (y)⁰ + C (7,1) x (3)⁶ x (y)¹ + C (7,2) x (3)⁵ x (y)² + C (7,3) x (3)⁴ x (y)³ + C (7,4) x (3)³ x (y)⁴ +.......... C (7,7) x (3)⁰ x (y)⁷
C (7,4) x (3)³ x (y)⁴
= x 27 x y⁴
=945 y⁴
jadi suku ke lima (3+y)⁷ adalah ---> 945 y⁴