Y=-2x² - график красный
у=4х - график зеленый
X1+x2=-19
x1*x2=48
x1=-16
x2=-3
<span>x</span>²<span>+19x+48=(x+16)*(x+3)</span>
(b+c-2a)(c-b)+(c+a-2b)(a-c)-(a+b-2c)(a-b)=
=bc+c²-2ac-b²-bc+2ab+ac+a²-2ab-c²-ac+2bc-a²-ab+2ac+ab+b²-2bc=
=(bc-bc+2bc-2bc)+(ac-ac+2ac-2ac)+(ab-ab+2ab-2ab)+(a²-a²+b²-b²+c²-c²)≡0.