algebra 2 problem

Question

f(x) =x³ -8x² +9x -72 ; zero: -3i

Answer 1

Factor by grouping and solve.

 

x³ - 8x² + 9x - 72 = 0

 

x²(x - 8) + 9(x - 8) = 0

 

(x² + 9)(x - 8) = 0

 

x² + 9 = 0 or x - 8 = 0

 

x = ±3i or x = 8