help math

A square sheet of paper ABCD is folded such that B falls on the midpoint M of CD. In what ratio does the crease divide BC?

A square sheet of paper ABCD is folded such that B falls on the midpoint M of CD. In what ratio does the crease divide BC?

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

BC = 4           y = 4 - x          z = 2

Using Omi's diagram we have:

x² = y² - z²              x = sqrt{ (4 - x)² - 2²}             x = 1.5

Ratio  y : x = 5 : 3