If un = 1 - 1 , then the value of u1 + u2 + u3 + u4 + u5

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u_n =	1	-	1
	n		n + 1

∴ u₁ =	1	-	1
	1		1 + 1

⇒ u₁ = 1 -	1	;
	2

Similarlly ,u₂ =	1	-	1	;
	2		3

u₃ =	1	-	1	;
	3		4

u₄ =	1	-	1	;
	4		5

u₅ =	1	-	1
	5		6

∴ u₁ + u₂ + u₃ + u₄ + u₅ = 1 -	1	+	1	-	1	+	1	-	1	+	1	-	1	+	1	-	1
	2		2		3		3		4		4		5		5		6

u₁ + u₂ + u₃ + u₄ + u₅ = 1 -	1	=	6 - 1
	6		6

Hence , u₁ + u₂ + u₃ + u₄ + u₅ =	5
	6

If u_n =	1	-	1	, then the value of u₁ + u₂ + u₃ + u₄ + u₅ is
	n		n + 1