a: f(x)=3x^3+6x^2+x-2x^2-7=3x^3+4x^2+x-7
\(g\left(x\right)=3x^3-2x^2+5x+7x^2+3=3x^3+5x^2+5x+3\)
b: M(x)=2*f(x)+G(x)
=6x^3+8x^2+2x-14+3x^3+5x^2+5x+3
=9x^3+13x^2+7x-11
N(x)=G(x)-F(x)
=3x^3+5x^2+5x+3-3x^3-4x^2-x+7
=x^2+4x+10
c: x^2-3x=0
=>x=0 hoặc x=3
M(x)=9x^3+13x^2+7x-11
M(0)=0+0+0-11=-11
M(3)=9*3^3+13*3^2+7*3-11=370
d: N(x)=x^2+4x+10
=(x+2)^2+6>=6
Dấu = xảy ra khi x=-2


