a) f(x)=x
x > 0 CRESCENTE
x=0 constante
x<0 decrescente
b)f(x)=2x+4
2X+4>0 ==> x > -2 crescente
x= - 2 constante
x < -2 decrescente
c)f(x)=-3x+1
-3x+1>0 ==> x < 1/3 crescente
x= 1/3 constante
x > 1/3 decrescente
d)f(x)=-2x
-2x>0 ==> x < 0 crescente
x=0 constante
x > 0 decrescente
