The polynomial \(x^3 - 2x + a\), where \(a\) is a constant, is denoted by \(p(x)\). It is given that \((x + 2)\) is a factor of \(p(x)\).
(i) Find the value of \(a\).
(ii) When \(a\) has this value, find the quadratic factor of \(p(x)\).
Solution
(i) Since \((x + 2)\) is a factor of \(p(x)\), substituting \(x = -2\) into \(p(x)\) should yield zero:
\((-2)^3 - 2(-2) + a = 0\)
\(-8 + 4 + a = 0\)
\(a = 4\)
(ii) With \(a = 4\), the polynomial becomes \(x^3 - 2x + 4\). To find the quadratic factor, divide \(x^3 - 2x + 4\) by \(x + 2\):
Perform polynomial division:
\(x^3 - 2x + 4 = (x + 2)(x^2 - 2x + 2)\)
Thus, the quadratic factor is \(x^2 - 2x + 2\).
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