First divide by 3 because we don't want any factor in front of the x² when doing factorization:
3x² + 15x – 18 = 0 => x² + 5 - 6 = 0
Then find the two numbers that multiply to -6 and add up to +5:
x² + 5 - 6 = 0 => (x-1)(x+6) = 0
So the solutions are x=1 or x=-6, that's answer B.
