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tmua.me Medium Set E Paper 2 · Q17

Paper 2Logic & proofNumber & countingAlgebra

The polynomial

f(x)=x3+ax2+bx+cf(x)=x^3+ax^2+bx+c

has integer coefficients, and both f(0)f(0) and f(1)f(1) are odd integers.

You may use the fact that any rational root of a polynomial with integer coefficients and leading coefficient 11 is an integer.

Consider the statements

  • I. f(n)f(n) is odd for every integer nn.
  • II. Every real root of f(x)=0f(x)=0 is irrational.
  • III. The equation f(x)=0f(x)=0 has exactly one real root.

Which of these statements must be true?

ANone of them
BI\mathrm{I} only
CII\mathrm{II} only
DIII\mathrm{III} only
EI\mathrm{I} and III\mathrm{III} only
FI\mathrm{I} and II\mathrm{II} only
GII\mathrm{II} and III\mathrm{III} only
HI\mathrm{I}, II\mathrm{II} and III\mathrm{III}

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