Solve the b) , and please with details

Question

Solve the b) , and please with details

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Answer 1

2x³ - x² - 18x + 9 = x²(2x - 1) - 9(2x - 1) = (x² - 9)(2x - 1) = (x - 3)(x + 3)(2x - 1) = 
(x - 3)(2x² - x + 6x - 3) = (x - 3)(2x² + 5x - 3)
a = 2
b = 5
c = -3