Лови//77777///////77777777
<span>по формуле:</span>
<span> sin (альфа минус бетта)= sin альфа cos бетта -cos альфа sin бетта </span>
<span><span>sin40°cos10°-cos40°sin10° = sin (40*-10*)= sin 30 *= 0,5</span></span>
x1^2 + x2^2 = (x1+x2)^2 - 2x1x2
По теореме Виета x1+x2 = 6 и x1x2 = 4
Значит, x1^2+x2^2 = 36 - 2*4 = 28.
Скорость катера = х км/час
Скорость против течения = (х-1) км/час
Скорость по течению = (х+1) км/час
Уравнение:
![S=V\cdot t\; \; \Rightarrwo \; \; t=\frac{S}{V}\\\\ \frac{15}{x-1} + \frac{14}{x+1} = \frac{30}{x} \\\\ \frac{15x+15+14x-14}{(x-1)(x+1)} = \frac{30}{x} \\\\ \frac{29x+1}{x^2-1} - \frac{30}{x} =0\\\\ \frac{-(x^2-x-30)}{x^1-1} =0\\\\x^2-x-30=0\; \; \to \; \; x_1=-5\; \; ne\; podxjdit\; ,\; x_2=6\\\\Otvet:\; \; V_{katera}=6\; km/chas](https://tex.z-dn.net/?f=S%3DV%5Ccdot+t%5C%3B+%5C%3B+%5CRightarrwo+%5C%3B+%5C%3B+t%3D%5Cfrac%7BS%7D%7BV%7D%5C%5C%5C%5C+%5Cfrac%7B15%7D%7Bx-1%7D+%2B+%5Cfrac%7B14%7D%7Bx%2B1%7D+%3D+%5Cfrac%7B30%7D%7Bx%7D+%5C%5C%5C%5C+%5Cfrac%7B15x%2B15%2B14x-14%7D%7B%28x-1%29%28x%2B1%29%7D+%3D+%5Cfrac%7B30%7D%7Bx%7D+%5C%5C%5C%5C+%5Cfrac%7B29x%2B1%7D%7Bx%5E2-1%7D+-+%5Cfrac%7B30%7D%7Bx%7D+%3D0%5C%5C%5C%5C+%5Cfrac%7B-%28x%5E2-x-30%29%7D%7Bx%5E1-1%7D+%3D0%5C%5C%5C%5Cx%5E2-x-30%3D0%5C%3B+%5C%3B+%5Cto+%5C%3B+%5C%3B+x_1%3D-5%5C%3B+%5C%3B+ne%5C%3B+podxjdit%5C%3B+%2C%5C%3B+x_2%3D6%5C%5C%5C%5COtvet%3A%5C%3B+%5C%3B+V_%7Bkatera%7D%3D6%5C%3B+km%2Fchas)
3х-1 = 5(х+2)-х
3x-1=5x+10-x
3x-5x+x-1-10=0
-x-11=0/*(-1)
x+11=0
x=-11