Ответ:
f'(x) = (2*x+8)*(2-1) = 2x + 8
4 62 4*3 - 62 12-62 50 2
--- - ---- = ----------- = ------- = - ---- = - --
25 75 75 75 75 3
3 1 3+ 1*2 3+2 5 1
4-- + 7-- = 11--------- = 11----- = 11-- = 12--
4 2 4 4 4 4
3 2 49 49 1
-- * (- --) * --- = - --- = -24-- = -24,5
1 3 4 2 2
![\displaystyle \left \{ {{a_1+a_2+a_3=12} \atop {a_1\cdot a_2=8}} \right. \Rightarrow \left \{ {{a_1+a_1+d+a_1+2d=12} \atop {a_1\cdot(a_1+d)=8}} \right. \Rightarrow\\ \\ \left \{ {{3a_1+3d=12|:3} \atop {a_1(a_1+d)=8}} \right. \Rightarrow \left \{ {{a_1+d=4} \atop {a_1\cdot 4=8}} \right. \Rightarrow \left \{ {{d=2} \atop {a_1=2}} \right.](https://tex.z-dn.net/?f=%5Cdisplaystyle++%5Cleft+%5C%7B+%7B%7Ba_1%2Ba_2%2Ba_3%3D12%7D+%5Catop+%7Ba_1%5Ccdot+a_2%3D8%7D%7D+%5Cright.+%5CRightarrow+%5Cleft+%5C%7B+%7B%7Ba_1%2Ba_1%2Bd%2Ba_1%2B2d%3D12%7D+%5Catop+%7Ba_1%5Ccdot%28a_1%2Bd%29%3D8%7D%7D+%5Cright.+%5CRightarrow%5C%5C+%5C%5C++%5Cleft+%5C%7B+%7B%7B3a_1%2B3d%3D12%7C%3A3%7D+%5Catop+%7Ba_1%28a_1%2Bd%29%3D8%7D%7D+%5Cright.+%5CRightarrow+%5Cleft+%5C%7B+%7B%7Ba_1%2Bd%3D4%7D+%5Catop+%7Ba_1%5Ccdot+4%3D8%7D%7D+%5Cright.+%5CRightarrow+%5Cleft+%5C%7B+%7B%7Bd%3D2%7D+%5Catop+%7Ba_1%3D2%7D%7D+%5Cright.+)
Итак, первое число равен 2, тогда второе - (2+2=4), а третье - (2+2*2)=6
2)нужно приравнять уравнения:5/x=x=4
5=x^2+4x
x^2+4x-5=0
решая уравнение по теореме Виета:х1=-5, х2=1 тогда у1=-1,у2=5
(-5;-1) (1;5)