решите пожалуйста и если можно какую нибудь задачу со-2ой части
скорость течения = x км/ч
по течению =х+10
против=х-10
все время =20/3ч=время по теченю+против+стоянка
2км/ч
![\[\begin{array}{l} \frac{{20}}{3} = \frac{5}{3} + \frac{{24}}{{10 + x}} + \frac{{24}}{{10 - x}}\\ \frac{{15}}{3} = \frac{{24}}{{10 + x}} + \frac{{24}}{{10 - x}}\\ 5\left( {10 + x} \right)\left( {10 - x} \right) = 24\left( {10 - x} \right) + 24\left( {10 + x} \right)\\ 5\left( {100 - {x^2}} \right) = 240 - 24x + 240 + 24x\\ 500 - 5{x^2} = 480\\ 5{x^2} = 20\\ {x^2} = 4\\ x = \pm 2 \end{array}\]](https://tex.z-dn.net/?f=%5C%5B%5Cbegin%7Barray%7D%7Bl%7D+%5Cfrac%7B%7B20%7D%7D%7B3%7D+%3D+%5Cfrac%7B5%7D%7B3%7D+%2B+%5Cfrac%7B%7B24%7D%7D%7B%7B10+%2B+x%7D%7D+%2B+%5Cfrac%7B%7B24%7D%7D%7B%7B10+-+x%7D%7D%5C%5C+%5Cfrac%7B%7B15%7D%7D%7B3%7D+%3D+%5Cfrac%7B%7B24%7D%7D%7B%7B10+%2B+x%7D%7D+%2B+%5Cfrac%7B%7B24%7D%7D%7B%7B10+-+x%7D%7D%5C%5C+5%5Cleft%28+%7B10+%2B+x%7D+%5Cright%29%5Cleft%28+%7B10+-+x%7D+%5Cright%29+%3D+24%5Cleft%28+%7B10+-+x%7D+%5Cright%29+%2B+24%5Cleft%28+%7B10+%2B+x%7D+%5Cright%29%5C%5C+5%5Cleft%28+%7B100+-+%7Bx%5E2%7D%7D+%5Cright%29+%3D+240+-+24x+%2B+240+%2B+24x%5C%5C+500+-+5%7Bx%5E2%7D+%3D+480%5C%5C+5%7Bx%5E2%7D+%3D+20%5C%5C+%7Bx%5E2%7D+%3D+4%5C%5C+x+%3D+%5Cpm+2+%5Cend%7Barray%7D%5C%5D "\[\begin{array}{l} \frac{{20}}{3} = \frac{5}{3} + \frac{{24}}{{10 + x}} + \frac{{24}}{{10 - x}}\\ \frac{{15}}{3} = \frac{{24}}{{10 + x}} + \frac{{24}}{{10 - x}}\\ 5\left( {10 + x} \right)\left( {10 - x} \right) = 24\left( {10 - x} \right) + 24\left( {10 + x} \right)\\ 5\left( {100 - {x^2}} \right) = 240 - 24x + 240 + 24x\\ 500 - 5{x^2} = 480\\ 5{x^2} = 20\\ {x^2} = 4\\ x = \pm 2 \end{array}\]")