Resposta :
Espero ter ajudado, qualquer duvida só chamar ;)
a) f(-1)=9
f(-1)=5*(-1)-4
5*(-1)-4
-5-4
-9
b) f(3/5)= -5
f(3/5)=5(3/5)-4
15/5-4
15/5-20/5
15-20
-5
c) x=2
f(x)=5x-4
6=5x-4
6+4=5x
x=10/5
x=2
d) x= 5/4
f(x)=5x-4
0=5x-4
5x=4
x=5/4
a) f(-1)=9
f(-1)=5*(-1)-4
5*(-1)-4
-5-4
-9
b) f(3/5)= -5
f(3/5)=5(3/5)-4
15/5-4
15/5-20/5
15-20
-5
c) x=2
f(x)=5x-4
6=5x-4
6+4=5x
x=10/5
x=2
d) x= 5/4
f(x)=5x-4
0=5x-4
5x=4
x=5/4