7x^6+4x^3
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(1-x)³=1-3х+3х²-х³
<span>
(x-5y)³=х³-3х²·(5у)+3х·25у²-125у³=х³-15х²у+75ху²-125у³</span>
<span>Обозначим за х - цену 1 тетради , и у - цену 1 альбома .</span>
<span>Составим систему уравнений. </span>
<span>8х+5у=9 </span>
<span>4х+4=6у </span>
<span>5у=9-8х </span>
<span>у= ( 9-8х) / 5 </span>
<span>4х+4 = (6(9-8х)) / 5 </span>
<span>20х+20=54-48х </span>
<span>68х=34 </span>
<span>х = 0.5 </span>
<span>у = (9-8х) / 5 = (9-4) / 5 </span>
<span>у= 1 </span>
<span>Ответ: х = 0.5 , у = 1</span>