Math, asked by gopal46, 1 year ago

how many teams of an ap 9,17,25 ....must be taken to give a sum of 636

Answers

Answered by Sanaya625
2
a=9 , d=8 ,Sn = 636
Sn = n/2[2a + (n-1)d]
636 = n/2[18 + (n-1)d]
now solve and calculate the value of n

reusmohammed: Sir can u Pls show me the full answer I want to check whether my steps are correct... Pls sir
Sanaya625: 636 = n/2[18+8n-8] , 636 = n/2[10+8n] , 636 = 5n+4n^2 , 4n^2 + 5n = 636
Sanaya625: Then factroise it
Answered by Anonymous
4

\bf\huge\boxed{\boxed{\bf\huge\:Hello\:Mate}}}



\bf\huge Let: first\: term\; be\: a \:and\: CD\: = 17 - 9 = 8



\bf\huge => S_{n} = 636



\bf\huge => \frac{N}{2}[2a + (n - 1)d] = 636



\bf\huge => \frac{N}{2}[2\times 9 + (n - 1)8] = 636



\bf\huge => \frac{N}{2} (8n - 10) = 636



\bf\huge => n(4n + 5) = 636



\bf\huge => 4n^2 + 5n + 636 = 0



\bf\huge => n = \frac{-5 + \sqrt{25 - 4\times 4\times -636}}{2\times 4}



\bf\huge = \frac{-5 + \sqrt{25 + 10176}}{8}



\bf\huge = \frac{- 5 + \sqrt{10201}}{8}



\bf\huge = \frac{-5 + 101}{8}



\bf\huge = \frac{96}{8} , \frac{-106}{8}



\bf\huge = 12 , \frac{-53}{4}



\bf\huge But\: n \:cannot\: be\: Negative



\bf\huge => n = 12



\bf\huge Hence\:Sum\: of\: 12\: terms\: is\: 636




\bf\huge\boxed{\boxed{\:Regards=\:Yash\:Raj}}}


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