(-2х-5х^2)(4-х)
-8х+2х^2-20х^2+5х^3
-8х-18х^2+5х^3
х (-8-18х+5х^2)=0
×=0 5х^2-18х-8=0
Д=(-18)^2-4*5 *(-8)=324+160=484
х1/2=18+-22/10
х1=4
х2=15.8
5х²-10х+50=3х²-34х-20
5х²-10х+50-3х²+34х+20=0
2х²+24х+70=0 (:2)
х²+12х+35=0
Д=144-140=4=корень из 2
х1=-12+2/2=-5
х2=-12-2/2=-7
У - 2х = 6
Х^2 - ху + у^2 = 12
Решение
у = 2х + 6
Х^2 - х( 2х + 6 ) + ( 2х + 6 )^2 = 12
X^2 - 2x^2 - 6x + 4x^2 + 24x + 36 = 12
3x^2 + 18x + 24 = 0
3( x^2 + 6x + 8 ) = 0
D = 36 - 32 = 4 = 2^2
X1 = ( - 6 + 2 ) : 2 = - 2
X2 = ( - 6 - 2 ) : 2 = - 4
y1 = 2•( - 2 ) + 6 = - 4 + 6 = 2
y2 = 2•( - 4 ) + 6 = - 8 + 6 = - 2
Ответ ( - 2 ; 2 ) ; ( - 4 ; - 2 )