Question

In an A.P., T1=22, Tn=-11, Sn=66 then find n?
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Answer 1

Step-by-step explanation:

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Answer 2

Step-by-step explanation:

Tn=-11 ,T1=22

a1=22

Tn= -11

a+(n-1) d= -11

22+(n-1)d= -11

(n-1) d = -11-22

(n-1) d= -33 ......(1)

Sn =66

n/2{2a+(n-1)d}=66

n{2a+(n-1) d}=66×2

n{2a+(n-1) d}=132

n{2×22+(-33)}=132 (using eqn1)

n(44-33) =132

n(11) =132

n=132/11

•:n=12