If sn=4n-n2 find it's 11th term
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Step-by-step explanation:
Sn=4n-n²
n(2a+(n-1)d)=n(4-n)
2
2a+(n-1)d=8-n
2a-d+nd=8-n
nd= -n. 2a-d=8
d= -1 2a+1=8
2a=7
a=7/2
Tn=a+(n-1)d
T11=7/2+(11-1)(-1)
=7/2-10
= -13/2
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