How many terms of the sequence -12,-9,-6,-3 must be taken to make the sum 54.
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Sn=54
a1=-12
d=a2-a1
= 3
so,
Sn=n/2{2a+(n-1)×d}
54=n/2{2×-12+(n-1)×3}
by solving we will get
n=12 and n=-3
since -3 cannot be a possible value
so,. n = 12
a1=-12
d=a2-a1
= 3
so,
Sn=n/2{2a+(n-1)×d}
54=n/2{2×-12+(n-1)×3}
by solving we will get
n=12 and n=-3
since -3 cannot be a possible value
so,. n = 12
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