3,5-2x+7,5=6х-(6*5*6*(-2))*(-7х*5*(-2))=6х-(30*12)*(70)=дальше сами(вроде так)
По формуле бинома Ньютона
![(2x-y)^5=\displaystyle \sum^{5}_{k=0}C^k_5\cdot (2x)^{5-k}\cdot (-y)^k](https://tex.z-dn.net/?f=%282x-y%29%5E5%3D%5Cdisplaystyle%20%5Csum%5E%7B5%7D_%7Bk%3D0%7DC%5Ek_5%5Ccdot%20%282x%29%5E%7B5-k%7D%5Ccdot%20%28-y%29%5Ek)
Найдем второй и четвертый член разложения при k = 1 и k = 3![a_2=C^1_{5}\cdot (2x)^{5-1}\cdot (-y)^1=-5\cdot 16x^4y=-80x^4y\\ \\ a_4=C^3_5\cdot (2x)^{5-3}\cdot (-y)^3=\dfrac{5!}{3!2!}\cdot 4x^2\cdot (-y^3)=-40x^2y^3](https://tex.z-dn.net/?f=a_2%3DC%5E1_%7B5%7D%5Ccdot%20%282x%29%5E%7B5-1%7D%5Ccdot%20%28-y%29%5E1%3D-5%5Ccdot%2016x%5E4y%3D-80x%5E4y%5C%5C%20%5C%5C%20a_4%3DC%5E3_5%5Ccdot%20%282x%29%5E%7B5-3%7D%5Ccdot%20%28-y%29%5E3%3D%5Cdfrac%7B5%21%7D%7B3%212%21%7D%5Ccdot%204x%5E2%5Ccdot%20%28-y%5E3%29%3D-40x%5E2y%5E3)
2) ![A^2_x=42](https://tex.z-dn.net/?f=A%5E2_x%3D42)
![\dfrac{x!}{(x-2)!}=42~~~~\Rightarrow~~~~\dfrac{(x-2)!\cdot (x-1)x}{(x-2)!}=42\\ \\ x(x-1)=42\\ \\ x^2-x-42=0](https://tex.z-dn.net/?f=%5Cdfrac%7Bx%21%7D%7B%28x-2%29%21%7D%3D42~~~~%5CRightarrow~~~~%5Cdfrac%7B%28x-2%29%21%5Ccdot%20%28x-1%29x%7D%7B%28x-2%29%21%7D%3D42%5C%5C%20%5C%5C%20x%28x-1%29%3D42%5C%5C%20%5C%5C%20x%5E2-x-42%3D0)
По теореме Виета
— посторонний корень;
![x_2=7](https://tex.z-dn.net/?f=x_2%3D7)
Ответ: 7.
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1) 3 и 5 переводим в дестичную дробь: 3/1 и 5/1
2) 1 1/2=3/2
3) 1 1/4=5/4
4) 3/1:3/2=3/1*2/3=2
5) 5/1:5/4=5/1*4/5=4
6) 2+4=6
Ответ: 6