i have an assignment question hopefully someone can help me with or point me in the right direction....

the question comes in 3 parts.i have done parts (i),(ii) i need to work out the.3rd part(iii)

(ii) if the roots of a cubic equation are x= -5/2 , x= 1/4, x= 3

determine the cubic expression by expansion, with these roots.

(iii) if x = Cos(2ω) in part (ii) of this question where ω is measured in radians. determine the values of ω, that satisfy the roots given that

0 ≤ ω ≥ 2(pi)

any help much appreciated

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