9x² = -15x
9x² + 15x = 0
x = -b ± √b² - 4ac / 2a
x = -15 ± √15² - 4 (9) (0) / 2(9)
x = -15 ± √225/18
x = -15 ± 15/18
x1 = -15 + 15/18 = 0/18
x2 = - 15 - 15/18 = -5/3
Comprobación
9x² + 15x = 0
9 (0/18)² + 15 (0/18) = 0
9 (0/234) + 15 (0) = 0
9 (0) + 15 (0) = 0
0 = 0
9x² + 15x = 0
9(-5/3)² + 15 (-5/3) = 0
9 (25/9) - 25 = 0
25 - 25 = 0
0 = 0
Espero haberte ayudado. Suerte en los estudios ≧◠◡◠≦.