Question

Which term in A.P 10,8,6, ...... is -28?

Answer 1

$\blue{\bold{\underline{\underline{Answer:}}}}$

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$\green{\underline \bold{Given :}}$

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• An A.P 10 , 8 , 6 ,........

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$\red{\underline \bold{To \: Find:}}$

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• Which term in A.P is -28

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$\large{\orange{\underline{\tt{Solution :-}}}}$

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$\underline{\bold{\texttt{We know that :}}}$

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$\purple\longrightarrow$ $\bf a_n = a + (n - 1)d$

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• $\rm a_n$ = nth term = -28

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• a = First term of the AP = 10

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• n = number of term = n

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• d = Common difference = 8 - 10 = -2

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$\underline{\bold {\texttt{Putting all the values ,}}}$

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$\sf \longmapsto -28 = 10 + (n - 1)-2$

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$\sf \longmapsto -28 = 10 - 2n + 2$

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$\sf \longmapsto -28 = 12 - 2n$

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$\underline{\bold{\texttt{Dividing the above equation by 2}}}$

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$\sf \longmapsto -14 = 6 - n$

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$\sf \longmapsto n = 6 + 14$

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$\bf \dashrightarrow n = 20$

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Hence -28 is 20th term in the given AP

$\rule{200}5$