Hi Juan, try sum-and-product method. If that doesn't work try quadratic formula [-b+/-sqrt(b2-4ac)]/2a.
Are there two numbers that add up to 5 and give you 18 when multiplied?
18*1
9*2
3*3*2
It appears there are no two such numbers.
Now you go to the quadratic formula and here is the key to using it in this case - you don't have to use the whole formula. You can just use the determinant b2-4ac and get to the answer you are looking for.
52-4*2*9=-47
That means you have complex roots, two complex roots