Determine o sinal do produto:

a) ( + ) . ( + ) = f) ( + ) . ( – ) =

b) ( – ) . ( – ) = g) ( + ) . ( + ) . ( + ) =

c) ( + ) . ( – ) . ( – ) = h) ( – ) . ( + ) . ( + ) =

d) ( – ) . ( – ) . ( – ) = i) ( – ) . ( + ) . ( – ) . ( + ) =

e) ( – ) . ( – ) . ( – ) . ( – ) = j) ( – ) . ( – ) . ( – ) . ( – ) . ( – ) =