Arithmetic Sequence: Given the first element 19/7 and the common difference -2/7 and the Sn(arithmetic series) 13. Find the value of the nth element and the value of N

Question

anonymous · Answer

$$a _{1}=19/7$$

anonymous · Answer

$$\huge s _{n}=13$$

anonymous · Answer

$$\huge a _{n}$$ is the nth element.

anonymous · Answer

what do u think?

anonymous · Answer

formulas: $$\huge s _{n}=(N/2)(a _{1}+a _{n})$$

anonymous · Answer

$$\huge a _{n}= a _{1} + (N-1)d$$

anonymous · Answer

u had to find nth element so will apply this formula $$_{Sn}=n/2(2a+(n-1)d)$$

anonymous · Answer

ok. then what? :(

anonymous · Answer

this is part of our quiz and i didnt get the correct answer. thats why im asking for help because our exam is tomorrow

anonymous · Answer

then after u will get a quadratic equation in terms of n. So u had solve for n.

anonymous · Answer

$$(−34N2+490N−3094)/119$$

anonymous · Answer

$$n^{2}-20n+91$$ will get this equation

anonymous · Answer

how did you get that? :((

anonymous · Answer

please show me the soln. :(

anonymous · Answer

oh. shoot.i wrote something wrong in the given. a sub 1 should be equal to 19/17

anonymous · Answer

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