1³-2³+3³-4³+....+9³ =

S=13-23+33-43+...+93=13+33+....+93-23+43+....+83S=an-bnan=2n-13 , bn=2n3an=2n-13=8n3-12n2+6n-1=8nn+122-12nn+12n+16+6nn+12-n=855+122-1255+110+16+655+12-5=83022-10611+156-5=8225-660+90-5=1800-665+90=1225bn=2n3=8n3=844+122=82022=8100=800s=1229-800=449   ANS...

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