Question 173413
p^2 + 3p - 9 = 0
p^2 + 3p = 9
Halve the 'b' coefficient (3) to get 3/2 and then square it (9/4)--add to both sides: 
p^2 + 3p + 9/4 = 9 + 9/4
(p + 3/2)^2 = 36/4 + 9/4
(p + 3/2)^2 = 45/4
p + 3/2 = sqrt(45/4)
p + 3/2 = (1/2)sqrt(45)
p + 3/2 = (1/2)sqrt(3*3*5)
p + 3/2 = (3/2)sqrt(5)
p = (3/2)sqrt(5) - 3/2
p = 1.8541