u5=648=ar^4
----------------------- >>>> =r"=9 , r=3
u3=72=ar^2
a.
ar"=72
a=72/9=8
b.S5
=a(r^5-1)/r-1
=8(3^5-1)/3-1
=8(243-1)/2
=968
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u5=648=ar^4
----------------------- >>>> =r"=9 , r=3
u3=72=ar^2
a.
ar"=72
a=72/9=8
b.S5
=a(r^5-1)/r-1
=8(3^5-1)/3-1
=8(243-1)/2
=968