1+2d+q^4=21
1+4d+q^2=13
d=2
q=2
an=1+(n-1)*2=2n-1
bn=2^(n-1)
设｛an｝是等差数列 ｛bn｝是各项都为正数的等比数列 且a1等于b1等于1 a3加b5等于21 a5加b3等于13 （
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