+0  
 
+1
66
1
avatar+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.

 Jun 2, 2021
 #1
avatar+119788 
+1

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 

 

 

cool cool cool

 Jun 2, 2021

42 Online Users

avatar
avatar
avatar