Answer:
1. 2,520,000 y^5.
2. 26730 x^7 y^8.
Step-by-step explanation:
1. (2y - 5)^9
(r + 1)th term of (a + b)^n = nCr a^(n-r) b^r
So the 5th, (4+1)th term, = 9C4 (2y)^(9-4) (-5)^4
= 126 * 2^5 * y^5 * 625
= 2,520,000 y^5.
2. ( x + 3y^2)^11.
5th term = 11C4 x^(11-4) (3y^2)^4
= 330*x^7*81*y^8.
= 26730 x^7 y^8.
