(x^2-3x+5)-(4x^2-2x-8)=2-x-x^2
X^2-3x+5-4x^2+2x+8=2-x-x^2
-3x^2-x+13=2-x-x^2
-3x^2+13=2-x^2
-3x^2+x^2=2-13
-2X^2= -11
x^2=11/2
x= +-√22/2
x= +√22/2
x= -√22/2
<span> f(x)=x^2+2x-8</span>
f(x)'=2x+2f(3)= 2*3+2=6+2=8
Ответ:8
вроде так