<span><span><span><span>x2</span>+<span>y2</span></span><span><span>−6</span>x</span></span><span><span>−8</span>y</span></span>=<span><span>−21</span>+<span>0
</span></span><span><span><span><span>x2</span>+<span>y2</span></span><span><span>−6</span>x</span></span><span><span>−8</span>y</span></span>=<span>−<span>21
</span></span><span><span>(<span>x<span>−3</span></span>)</span>2</span><span>−<span>9
</span></span><span><span><span><span><span>(<span>x<span>−3</span></span>)</span>2</span><span>−9</span></span>+<span>y2</span></span><span><span>−8</span>y</span></span>=<span>−<span>21
</span></span><span><span><span><span>(<span>x<span>−3</span></span>)</span>2</span>+<span>y2</span></span><span><span>−8</span>y</span></span>=<span><span>−21</span>+<span>9
</span></span><span><span>(<span>y<span>−4</span></span>)</span>2</span><span>−<span>16
</span></span><span><span><span><span>(<span>x<span>−3</span></span>)</span>2</span>+<span><span>(<span>y<span>−4</span></span>)</span>2</span></span><span>−16</span></span>=<span><span>−21</span>+<span>9
</span></span><span><span><span>(<span>x<span>−3</span></span>)</span>2</span><span><span>(<span>y<span>−4</span></span>)</span>2</span></span>=<span><span><span>−21</span>+9</span>+<span>16
</span></span><span><span><span>(<span>x<span>−3</span></span>)</span>2</span>+<span><span>(<span>y<span>−4</span></span>)</span>2</span></span>=<span><span>−12</span>+<span>16
</span></span><span><span><span>(<span>x<span>−3</span></span>)</span>2</span>+<span><span>(<span>y<span>−4</span></span>)</span>2</span></span>=<span>4</span>
На рисунке а и d - крайние члены пропорции, b и с - средние члены пропорции.
Свойство пропорции: произведение крайних членов равно произведению средних членов.
Пропорция будет верной, если
1) поменять местами крайние члены;
2) поменять местами средние члены;
3) выполнить одновременно две перестановки.
Если еще надо
масса в-ва в первом растворе: 250*0,12 =30 г
во втором: 250*0,24 = 60 г
в двух : 30+60=90
масса смешенного раствора: 250*2=500 г
концентрация нового раствора: 90/500 =0,18
Ответ: 18%
12000=100%
12000÷100%=120(1%)
120×15%=1800
12000×1800=13800
Ответ:13800руб.
