1.

How many terms of the AP -6,-11/2,5 are needed to give the sum 25?​

Answer»

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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