<span>Ответ 140 . Сто сорок,не меньше,не больше. 140 пиши в частное 140 </span>
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Решение
<span>x - y = 7 </span>
<span>x^2 + y^2 = 9 - 2xy </span>
<span>x - y = 7 </span>
<span>x^2 + 2xy + y^2=9 </span>
<span>x - y = 7 </span>
<span>(x + y)^2 =9 => x+y=3 и x+y= -3 </span>
<span>=> две новые системы уравнений: </span>
<span>1) x - y = 7 (1) </span>
<span>x + y = 3 (2) </span>
<span>Уравнение (1) + (2) => </span>
<span>2x = 10 => x=5 => y=x-7=5-7= -2 </span>
<span>2) x - y = 7 (1) </span>
<span>x + y = -3 (2) </span>
<span>Уравнение (1) + (2) => </span>
<span>2x = 4 => x=2 => y=x-7=2-7= -5 </span>
<span>Ответ: x1=5, y1= -2 и x2=2, y2= -5</span>
5+3=8 5+8=13 8-5=8 3+13=8
15*28*5 <span> 15*7*4*5 </span> = <span>7 </span>
_______ = 17*5*4*15 17
119*60