Resposta :
e-3f+5=-7 e-3f+5=-7
e-3f+5+7=0 e-3f+12=0
e-3f+12=0 -3f+12=-e
e+12=3f -3f=-e-12
e=3f-12 -f=-1/3.e-4 (-1)
f=1/3.e+4
e-3f+5+7=0 e-3f+12=0
e-3f+12=0 -3f+12=-e
e+12=3f -3f=-e-12
e=3f-12 -f=-1/3.e-4 (-1)
f=1/3.e+4