Answers

2016-08-02T20:05:20+08:00
A=lw;
420=lw;....a

l=3W-1.....b;
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420=[3w-1]w;
420=3w^2-w;
3w^2-w-420;

w=[1+71]/2(3)
w=72/6;
  =12 cm;..... ans.
l=3(12)-1;
 =36-1
 =35 cm........ans
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