Form a polynomial f(x) with real coefficients having the given degree and zeros

Question

21) Degree: 4, zeroes: 2i and -3i
22) Degree: 3, Zeroes i and -10

Answer 1

for every a+bi there is a a-bi solution

(x-2i)(x+2i)(x-3i)(x+3i) = 0

(x^2 +4)(x^2+9) = 0

x^4 + 13 x^2 + 36 = 0

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(x-i)(x+i)(x+10) = 0 etc