<span><span>31 / 3 × 41 / 5 + 4,2 × 2 / 3 + 31 / 3 × 24 / 5 + 2,8 × 2 / 3 = 31/3(41/5+24/5) +2/3(4,2+2,8)= 31/3*65/5+2/3*7=31/3*13+14/3= 403/13+14/3=417/3=139.
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Данное дифференциальное уравнение является уравнением с разделяющимися переменными.
![\displaystyle \int\frac{ydy}{1+y^2}=-\int\frac{xdx}{1+x^2}~~~\Rightarrow~~~\frac{1}{2}\int\frac{d(1+y^2)}{1+y^2}=-\frac{1}{2}\int\frac{d(1+x^2)}{1+x^2}\\ \\ \\ \ln(1+y^2)=-\ln(1+x^2)+\ln C~~~\Rightarrow~~~\ln(1+y^2)=\ln\bigg(\frac{C}{1+x^2}\bigg)\\ \\ 1+y^2=\frac{C}{1+x^2}~~~~\Rightarrow~~~ \boxed{y=\pm\sqrt{\frac{C}{1+x^2}-1}}](https://tex.z-dn.net/?f=%5Cdisplaystyle%20%5Cint%5Cfrac%7Bydy%7D%7B1%2By%5E2%7D%3D-%5Cint%5Cfrac%7Bxdx%7D%7B1%2Bx%5E2%7D~~~%5CRightarrow~~~%5Cfrac%7B1%7D%7B2%7D%5Cint%5Cfrac%7Bd%281%2By%5E2%29%7D%7B1%2By%5E2%7D%3D-%5Cfrac%7B1%7D%7B2%7D%5Cint%5Cfrac%7Bd%281%2Bx%5E2%29%7D%7B1%2Bx%5E2%7D%5C%5C%20%5C%5C%20%5C%5C%20%5Cln%281%2By%5E2%29%3D-%5Cln%281%2Bx%5E2%29%2B%5Cln%20C~~~%5CRightarrow~~~%5Cln%281%2By%5E2%29%3D%5Cln%5Cbigg%28%5Cfrac%7BC%7D%7B1%2Bx%5E2%7D%5Cbigg%29%5C%5C%20%5C%5C%201%2By%5E2%3D%5Cfrac%7BC%7D%7B1%2Bx%5E2%7D~~~~%5CRightarrow~~~%20%5Cboxed%7By%3D%5Cpm%5Csqrt%7B%5Cfrac%7BC%7D%7B1%2Bx%5E2%7D-1%7D%7D)
a5 = a1 + 4d; a3 = a1 + 2d
a1 + a5 = a1 + a1 + 4d = 2a1 + 4d = 10
2(a1 + 2d) = 2*a3 = 10
a3 = 5
Если будет, что-то непонятно, пиши.