B1=81, q=1/3,b6=?, s5=?
b6=b1.qˇ5, b6=81.(1/3)ˇ5=81.1/243=81/243=1/3
b6=1/3
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s5=b1.(qˇ5 -1)/(q-1)
s5=81.(1/243-1)/(1/3-1)=81.(-242/243)/(-2/3)=(-242/3).(-3/2)=
=242.3/3.2=121
s5=121
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(b2=27,b3=9,b4=3,b5=1
81+27+9+3+1=121)
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.................. ичрчрлажвднв
По маме - Матильда.
По папе - Изольда.
1) 12ab-5a-ab-6a=11ab-11a
2) 15x^3-10x^2-20x