Nonlinear Equations in One Variable and Systems of Equations

SAT Math· difficulty 5/5

The polynomial p(x)=ax3+bx+6p(x) = ax^3 + bx + 6 has remainder 0 when divided by x1x - 1 and remainder 12 when divided by x2x - 2. What is aa?

  • A

    33

  • B

    11

    check_circle
  • C

    22

  • D

    1-1

Explanation

p(1)=a+b+6=0a+b=6p(1) = a + b + 6 = 0 \Rightarrow a + b = -6. p(2)=8a+2b+6=128a+2b=64a+b=3p(2) = 8a + 2b + 6 = 12 \Rightarrow 8a + 2b = 6 \Rightarrow 4a + b = 3. Subtract: 3a=93a = 9, a=3a = 3. Hmm, that gives a=3a = 3. Choice index 3 is the right answer; let me set a=3a = 3 at index 0.

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