3х+8/2х+1=х-4
3х+8/2х-х=-5 /*2 (всё умножаем на два)
6х+8х-2х=-10
12х=-10/12
х=-10/12
X+y=3<span>X^2-xy-y^2=1
х=3-у
(3-у)</span>²-у(3-у)-у²=1
9-6у+у²-3у+у²-у²=1
у²-9у+8=0
у1=1
у2=8
х1=3-1=2
х2=3-8=-5
y = - (x^2+36)/x
y= -(x+36/x)=-x-36/x
y'=-1+36/x^2
-1+36/x^2=0
1-36/x^2=0
(x^2-36)/x^2=0
(x-6)(x+6)/x^2=0
x=-6;x=6;x=0
- + + -
-----(-6)------(0)-----(6)----->x => x=6 - точка максимума
V ^ ^ V