solve by completing the square

x^2-3x=4

please show work

x^2 - 2(3/2)x = 4

x^2 - 2(3/2)x + (3/2)^2 = 4 + (3/2)^2
(x-3/2)^2 = 25/4
(x-3/2)^2 = (5/2)^2
x - 3/2 = ±5/2
x = 3/2 ± 5/2 = -1 or 4