Solve the equation

Solve the equation for r:
3r³ + 12r² = 36r

3r³ + 12r² = 36r
3r³ + 12r² - 36r = 0 {subtracted 36r from both sides}
3r(r² + 4r - 12) = 0 {factored 3r out}
3r(r + 6)(r - 2) = 0 {factored into two binomials}
3r = 0 or r + 6 = 0 or r - 2 = 0 {set each factor equal to 0}
r = 0 or r = - 6 or r = 2 {solved each equation for r}

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