It is true that only half of the moon is always illuminated
by the sun. The reason why the moon
changes it phases is because Moon orbits around the Earth, and due to this some
areas of the half of the moon will not be lit by the sun.
1.35 x 10 to the power of 5 is 135000
Three Types of Solutions of a System of Linear Equations. There are three possible outcomes for a system of linear equations: one unique solution, infinitely many solutions, and no solution. This video shows an example of each type of outcome.