SOLUTION: find the independent term of x in the expansion of ((2x-(3/x^2))^6

Algebra ->  Permutations -> SOLUTION: find the independent term of x in the expansion of ((2x-(3/x^2))^6      Log On


   



Question 900270: find the independent term of x in the expansion of ((2x-(3/x^2))^6
Answer by Edwin McCravy(20054) About Me  (Show Source):
You can put this solution on YOUR website!
Every term of  %282x-%283%2Fx%5E2%29%5E%22%22%29%5E6

is of the form

%22C%286%2Ck%29%22%282x%29%5E%286-k%29%283%2Fx%5E2%29%5Ek, where k = 0,1,2,3,4,5,6

Write %282x%29%5E%286-k%29 as 2%5E%286-k%29x%5E%286-k%29
Write %283%2Fx%5E2%29 as 3x%5E%28-2%29

%22C%286%2Ck%29%222%5E%286-k%29x%5E%286-k%29%283x%5E%28-2%29%29%5Ek

Write %283x%5E%28-2%29%29%5Ek as 3%5Ek%2Ax%5E%28-2k%29

%22C%286%2Ck%29%222%5E%286-k%29x%5E%286-k%293%5Ek%2Ax%5E%28-2k%29

Rearrange the factors:

%22C%286%2Ck%29%222%5E%286-k%293%5Ek%2Ax%5E%286-k%29x%5E%28-2k%29

Add the exponents of x

%22C%286%2Ck%29%222%5E%286-k%293%5Ek%2Ax%5E%286-3k%29

For the term to be independent of x, the power of x
must be 0, since x0 = 1 which contains no x.
So we set the exponent of x equal to 0:

6-3k=0%7D%7D%0D%0A%7B%7B%7B-3k=-6
k=2

So we substitute k=2

%22C%286%2C2%29%222%5E%286-2%293%5E2%2Ax%5E%286-3%2A2%29




15%2A16%2A9%2Ax%5E0

2160%2A1

2160

Edwin