SOLUTION: prove that (x-1)(x^8+x^7+x^6+...+1)=x^9-1 without multiplying out the brackets.

Question 842116: prove that (x-1)(x^8+x^7+x^6+...+1)=x^9-1 without multiplying out the brackets.
Answer by Fombitz(32388) (Show Source): You can put this solution on YOUR website!
Look at the first two terms.

The two terms sum to remove all but the first and last terms.
Similarly when you complete the multiplication, all that will be left are
(x^9-x^8+x^8+x^7-x^7+...-x+x-1)

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