x = the number
(x + 3)² = 441 ← square of sum of number and 3 equals 441
(x + 3)(x + 3) = 441 ← squared binomial
x² + 6x + 9 = 441 ← foil method
x² + 6x  432 = 0 ← subtracted 441
(x + 24)(x  18) = 0 ← factored
x + 24 = 0 or x  18 = 0 ← set to zero
x = 24 or x = 18 ← solved
The negative real number is 24
*McGenius*
