Answer:
3
lazy approach was with a graphic plotting program, but you can also calculate it. with the pq-formula.
p = -6
q = 9
x = -p/2 +- sqrt( (p/2)² - q)
x = -(-6)/2 +- sqrt ( (-6/2)² - 9)
x = 3 +- sqrt(9-9)
x = 3 +- sqrt(0)
x = 3 +- 0
x = 3
