AP,an=4 ,d=2,sn= -14,n=?,a=?
tejasri2:
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Hi Friend !!!
Here is ur answer !!!
an = 4
d = 2
sn = -14
n = ?
a = ?
an = a+(n-1)d
4 = a+(n-1)2
4 = a+2n-2
a+2n = 2+4
a+2n = 6
a = 6-2n
sn = n/2(a+an)
-14 = n/2(6-2n + 4)
-28 = n(10-2n)
-28 = n(2(5-n))
-14 = 5n-n²
n2-5n-14 = 0
n²-7n+2n-14= 0
n(n-7)+2(n-7) = 0
(n-7)(n+2) =0
n = 7
a = 6-2n = 6-2(7)
= 6-14
= -8
Hope it helps u : )
Here is ur answer !!!
an = 4
d = 2
sn = -14
n = ?
a = ?
an = a+(n-1)d
4 = a+(n-1)2
4 = a+2n-2
a+2n = 2+4
a+2n = 6
a = 6-2n
sn = n/2(a+an)
-14 = n/2(6-2n + 4)
-28 = n(10-2n)
-28 = n(2(5-n))
-14 = 5n-n²
n2-5n-14 = 0
n²-7n+2n-14= 0
n(n-7)+2(n-7) = 0
(n-7)(n+2) =0
n = 7
a = 6-2n = 6-2(7)
= 6-14
= -8
Hope it helps u : )
thank you
u r most welcome
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