If x=a+ar+ar2+....∞,y=b−br+br2−....∞,andz=c+cr2+cr4+....∞,(r|>1,c≠0thenxyz= .
A
abc
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B
acb
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C
abc
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D
cab
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Solution
The correct option is Aabc x=a+ar+ar2+....∞,⇒x=a(1−1r)=arr−1y=b−br+br2−....∞⇒y=b(1−(−1r))=brr+1z=c+cr2+cr4+....∞,⇒z=c(1−1r2)=cr2r2−1⇒zc=r2r2−1.....(1]xy=arr−1×brr+1=abr2r2−1⇒xy=ab×zc⇒xyz=abc