How many terms of the AP -6,-11/2,5 are needed to give the sum 25?
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Step-by-step explanation:
AP = -6,-11/2,5
So, a1=-6 , a2=-11/2 , a3=5
d= a2-a1
=-11/2-(-6)
=-11+12/2
d=1/2
Sum = 25
Sum =n/2[2a+(n-1)d]
25 =n/2[-12+(n-1)1/2]
50=n[-12+1/2n-1/2]
=n[-25/2+1/2n]
50 =-25/2n+1/2n^2
100=-25n+1n^2
0=n^2-25n-100
Then,
Factorise it and you will Get 2 answer
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