Which of the sectarian churches conducts its services largely in silence and without ritual

The answer is: the Quakers.

Explanation:

In Quaker meetings, a group of people may remain silent for an hour or so. Sometimes somebody may speak briefly, but an hour can pass without anybody uttering a word. In this way they can get quiet minds and open themselves.

reflecting point a across the origin negates both of its coordinates.

b = (5, -4)