If quasars are powered by black holes, why are they so bright? If a black hole can swallow everything, even light, then how can a black hole power anything, particularly something as bright as a quasar. Why doesn't the black hole swallow the light of the quasar?

Are quasars formed when two black holes combine? 

I assumed it might be like an orange when we press it from middle then its juice comes out from both ends.

Is my assumption right...or is there another reason?
The light emitted isn't actually from the black hole itself but the swirling matter that surrounds it called the accretion disk. The light emitted from the accretion disk is far enough to escape from the pull of the quasar. A link from wikipedia sufficiently explains this:


  Quasars are believed to be powered by accretion of material into supermassive black holes in the nuclei of distant galaxies, making these luminous versions of the general class of objects known as active galaxies. Since light cannot escape the black holes, the escaping energy is actually generated outside the event horizon by gravitational stresses and immense friction on the incoming material.


I am supposing that part of the question, you are asking why quasars are brighter than black holes. That's because of the larger amount of in falling matter into the black hole creates greater friction thus more light.