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duestion il2 1 1wt(a) How many terms of 932 will make sum 72 4

Answer»

Given,a=2/9, r= (-1/3×9/2)= -3/2, Sn= 55/72, n=?

Sn=a(1-r^n)/(1-r)

55/72 = (2/9)[1-(-3/2)^n]/(1+3/2)

(55/72)×(9/2)×(5/2)=1-(-3/2)^n

275/32=1-(-3/2)^n

(-3/2)^n = 1–275/32 = (32–275)/32 = (-243)/32

or (-3/2)^n=(-3/2)^5

or n = 5 terms


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