2y=85-7x
y= (85-7x)/2
y=-2.5x
(85-7x)/2=-2.5x
85-7x= -5x
2x=85
x=42.5
y= -2.5*42.5=-106.25
(42.5; -106.25)
D= 9-5=4
230=(2*5+4n-4)*n)/2
460=10n+4n^2-4n
4n^2+6n-460=0
D=1849
X1=11.5
X2=10
<span>ответ:10</span>
Y-y1 = (y2-y1)/(x2-x1) . (x-x1)
y +2 = 12/3 .(x+1)
y+2 = 4(x+1), y+2 = 4x+4, y = 4x+2 ili 4x-y+2=0