Answers

2014-08-24T23:13:30+08:00
(x+y)³  =  x³+3x²y +3xy²+y³  >  should remember this by heart
let x = a    & y = 2b
thus
(a+2b)³  = a³ +3a²2b+3a(2b)²+(2b)³
              =  a³+6a²b+12ab²+8b³
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