a)
[tex](f\circ g)(x)=f(g(x))=f(2x+1)=(2x+1)^2-7(2x+1)+6=4x^2-10x[/tex]
b)
[tex](f\circ g)(x)=0\Rightarrow 4x^2-10x=0\Rightarrow2x(2x-5)=0\Rightarrow x=0\text{ sau }2x-5=0\Rightarrow x=0\text{ sau }x=\displaystyle\frac{5}{2}\\x\in\{0,\frac{5}{2}\}[/tex]
c)
[tex](g\circ f)(x)=g(f(x))=g(x^2-7x+6)=2(x^2-7x+6)+1=2x^2-14x+13[/tex]
d)
[tex](g\circ f)(x)=0\Rightarrow 2x^2-14x+13=0\\\Delta=196-106=92\\\sqrt{\Delta}=2\sqrt{23}\\\displaystyle x_{1,2}=\frac{14\pm2\sqrt{23}}{4}=\frac{7\pm\sqrt{23}}{2}[/tex]
