completing the square
7/2=3.5
3.5^2=12.25
add that to both sides
x²-7x+12.25+3=12.25
factor perfect square
(x-3.5)²+3=12.25
minus 3 both sides
(x-3.5)²=9.25
square root both sides
x-3.5=+/-√9.25
add 3.5 to both sides
x=3.5+/-√9.25
x=3.5+√9.25 or 3.5-√9.25