SOLUTION: Find the fourth term in the expansion of (2x-1)^6

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Question 398234: Find the fourth term in the expansion of (2x-1)^6
Found 3 solutions by Alan3354, stanbon, Edwin McCravy:
Answer by Alan3354(69443)   (Show Source): You can put this solution on YOUR website!
The coefficients from Pascal's Triangle are 1 6 15 20 15 6 1
--> 20*(2x)^3*(-1)
= - 160x^3
Answer by stanbon(75887)   (Show Source): You can put this solution on YOUR website!
Find the fourth term in the expansion of (2x-1)^6
----
6C3(2x)^3(-1)^3
---
= 20(8x^3)(-1)
---
= -160x^3
=================
Cheers,
Stan H.
Answer by Edwin McCravy(20055)   (Show Source): You can put this solution on YOUR website!
Find the fourth term in the expansion of (2x-1)^6

The Rth term in the expansion of (A + B)N

is C(N,R-1)AN-R+1BR-1.

Therefore substituting A=2x, B=-1, N=6, R=4,

C(6,4-1)(2x)6-4+1(-1)4-1.

C(6,3)(2x)3(-1)3.

20(2x)3(-1).

20(23x3)(-1).

20(8x3)(-1).

-160x3.

Edwin
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