The first and last term of G.P. are a and l respectively; r being its common ratio; then the number of terms in this G.P. is-
a.(​log l - log a)/log r     
​b.l - (log l - log a)/log r 
c.(log a - log l)/log r
​d.l + (log l - log a)/log r

dear student

first term of GP = alet it have n terms thennth term=lso, l=arn-1taking log on both sides, we getlogl=log(arn-1)=loga+log(rn-1)=loga+(n-1)logr(n-1)=logl-logalogrn=logl-logalogr+1


  • 2
Its 1+ (logl-loga)/logr
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