1) 4×7 =28 (чел.)
Ответ:28 человек могут сесть за семь столов
×*30=1000-730
×*30=270
×=270:30
×=9
____________
9*30=1000-730
270=270
<span>Пошаговое:
</span><span><span>(7+3y-x2y)⋅(-2xy)</span><span>=-<span>(7+<span>3y</span>-<span>x2y</span>)⋅2xy</span></span><span>=-(<span>7+<span>(<span>3-x2</span>)y</span></span>)⋅2xy</span><span>=-(<span>7+<span>y(<span>-x2+3</span>)</span></span>)⋅2xy</span><span>=-<span>(<span>y(-x2+3)+7</span>)⋅2xy</span></span><span>=-(<span><span>y(-x2+3)⋅2xy</span>+<span>7⋅2xy</span></span>)</span><span>=<span>-<span>y(-x2+3)⋅2xy</span>-7⋅2xy</span></span><span>=<span>-<span>2yxy(-x2+3)</span>-14xy</span></span><span>=<span>-14xy-2yxy(-x2+3)</span></span></span>