Answer me 37)b question
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As it is AP with first term -15 and common difference 2
sum = n/2 ( 2a + (n-1)d)
-55 = n/2 ( 2× -15 + (n-1)2)
-110 = n( -30 + 2n -2)
-110 = -30n + 2 n.n - 2n
-55= -15 n + n.n- n
n.n -16n +55 =0
n.n -5n -11n +55 = 0
n( n-5) -11( n-5) = 0
(n -11) = 0, (n-5)=0
n = 11 ,5
sum = n/2 ( 2a + (n-1)d)
-55 = n/2 ( 2× -15 + (n-1)2)
-110 = n( -30 + 2n -2)
-110 = -30n + 2 n.n - 2n
-55= -15 n + n.n- n
n.n -16n +55 =0
n.n -5n -11n +55 = 0
n( n-5) -11( n-5) = 0
(n -11) = 0, (n-5)=0
n = 11 ,5
sandralarisha:
Thank you
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