a)
[tex]f(x)=2x+6\\2x+6=0\\2x=-6\\x=-3[/tex]
b)
[tex]f(x)=4x-6\\4x-6=0\\4x=6\\x=\cfrac{6}{4}=1.5[/tex]
c)
[tex]f(x)=\cfrac{-6}{x^2}+1\\\cfrac{-6}{x^2}+1=0\\-6+x^2=0\\x^2=6\\x=-\sqrt{6}\ \lor\ x=\sqrt{6}[/tex]
d)
[tex]f(x)=x^2-4\\x^2-4=0\\x^2=4\\x=-2\ \lor\ x=2[/tex]
