+69 When (a + b)^5 is expanded using the Binomial Theorem for certain values of a and b, the second term is 15, and the third term is 50. Find the first term.
having trouble with this one... thanks in advance.
+129907 The second term is The third term is
C(5,1)a^4 b = 15 C(5,2)a^3 b^2 = 50
5a^4b = 15 10a^3 b^2 = 50
a^4b = 3 a^3b^2 = 5 (2)
b = 3 / a^4 (1)
Sub (1) into (2) and we have
a^3 ( 3 / a^4)^2 = 5
9a^3 / a^8 = 5
9/5 = a^8 / a^3
9/5 = a^5
a = fifth root (9/5)= (9/5)^(1/5)
The frirst term = C(5,0) [ (9/5)^(1/5)]^5 = 1 * (9/5) = 9/5
