Q186 · Practice questionTechnology-freeComplex familiar5 marks
QUESTION 186 (5 marks)
The polynomial has real coefficients a,b and zero .
a)[3 marks]
Determine a and b.
b)[2 marks]
Determine the remaining zeros and explain why no further zeros are possible.
WORKED SOLUTION
5 marksPractice marking scheme
ANSWER
(a) . (b) .
Worked solution
(a) The conjugate zero gives factor . Write . The constant term gives , so r=-5. Expansion yields .
(b) The other zeros are the conjugate and the real zero -5. Along with the given zero these are three distinct zeros, exhausting the degree-three polynomial.
Equivalent mathematically justified methods accepted.
Exact answers unless a decimal accuracy is specified.
Part a: Form the conjugate-pair factor.
Part a: Use the constant term to find r=-5.
Part a: Expand and determine both coefficients.
Part b: State both remaining zeros.
Part b: Account for all zeros using the degree.
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