The term in the expansion:
T ( k+1) = n C k * A^(n-k) * B^k.
In this case: n = 11, k + 1 = 8, so k = 7.
A = x, B = - 3 y
T 8 = 11 C 7 * x^(11-7) * ( - 3 y )^7 =
=( 11 *10 * 9 * 8 * 7 * 6 * 5 ) / ( 7 * 6 * 5 * 4 * 3 * 2 * 1 )* x^4 * ( - 2,187 y^7 ) =
= 330 * ( - 2,187 ) x^4 y^7 = - 721,710 x^4 y^7
Answer: The 8th term in expansion is
The "compound amount" formula is A = P(1+r/n)^(nt),
where P=original investment, r=interest rate as a decimal fraction; n=number of compounding periods, and t=number of years.
Then A = $12000 * (1+0.08/2)^(2*11)
= $12000(1.04)^(22) = $28,439.03 (answer)
