Which 2 Numbers When Multiplied Give You -42 But When Added Give You 9?

42 = 1*42 = 2*21 = 3*14 = 6*7
None of these factor pairs differ by 9, so the numbers will involve square roots. We can find them using the quadratic formula.
  X(9-x) = -42
  -x^2 + 9x = -42    (multiply it out)
  x^2 - 9x - 42 = 0    (put the equation into standard form)
  x = (-(-9) ±√((-9)^2 - 4(1)(-42)))/(2*1)    (use the quadratic formula)
  = (9 ±√(81+168))/2    (evaluate)
  = (9±√249)/2    (evaluate)
  ≈ {-3.3899, 12.3899}