$\displaystyle 11+13+15..........+(2n-1)=n^2 - x^2 $ x=? A) 3 B) 4 C) 5 D) 6 E) 7
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Originally Posted by OPETH $\displaystyle 11+13+15..........+(2n-1)=n^2 - x^2 $ x=? A) 3 B) 4 C) 5 D) 6 E) 7 Can you find the value of the left hand side by using the formula for the sum of an arithmetic series ......? a = 11, d = 2, number of terms = n - 5. Then equate the value of the left hand side to n^2 - x^2 and solve for x.
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