If you complete the square on x2 - 3x
x2 - 3x + 9/4 (divide -3 by 2 and square the result)
( x - 3/2 )2
So: x2 - 3x + 1 = ( x2 - 3x ) + 1
= ( x2 - 3x + 9/4 ) + 1 - 9/4 (if you add 9/4 to a side, you must also subtract it)
= ( x - 3/2 )2 - 5/4
Left for you to finish ...