ICSEClass XMathematicsFactorisation01 Mark2024 Easy

QQuestion

What must be subtracted from the polynomial x³ + x² − 2x + 1 so that the resulting polynomial is exactly divisible by (x − 3)?

(a) −31

(b) −30

(c) 30

(d) 31

Exam-ready answer 01 Mark

Answer

(d) 31

Explanation:

Let k be the number to be subtracted.

The resulting polynomial is x³ + x² − 2x + 1 − k.

For it to be divisible by (x − 3), put x = 3:

3³ + 3² − 2(3) + 1 − k = 0

⇒ 27 + 9 − 6 + 1 − k = 0

⇒ 31 − k = 0

⇒ k = 31

Therefore, 31 must be subtracted.

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