Posted by **Jonathan** on Monday, December 5, 2011 at 9:35am.

I need to use Pascal's Triangle to expand (x-1)^5

I know I use the fifth row but I'm not sure how to do it- I have a bunch of these and I'm really confused- Please help if you can-

- Algebra -
**Reiny**, Monday, December 5, 2011 at 10:31am
you know the expansion must look like

?x^5(-1)^0 + ?x^4(-1)^1 + ?x^3(-1)^2 + ?x^2(-1)^3 + ?x^1(-1)^4 + ?x^0(-1)^5

= ?x^5 - ?x^4 + ?x^3 - ?x^2 + ?x - ?

now the 5th row of the triangle has values:

1 5 10 10 5 1

put these in where the ?'s are and you are done

= x^5 - 5x^4 + 10x^3 - 10x^2 + 5x - 1

suppose you had

(x+2)^4

= **1**x^4 + **4**x^3(2) + **6**x^2(2^2) + **4**x(2^3) + **1**2^4

= x^4 + 8x^3 + 24x^2 + 32x + 16

- Algebra -
**Reiny**, Monday, December 5, 2011 at 10:33am
That last term in the 2nd last row of course is 1(2^4) or 16

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