Nonlinear Equations in One Variable and Systems of Equations

SAT Math· difficulty 5/5

The polynomial p(x)=x3+ax2+bx+2p(x) = x^3 + ax^2 + bx + 2 has x1x - 1 and x+2x + 2 as factors. What is the value of bb?

  • A

    00

  • B

    22

  • C

    11

  • D

    1-1

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Explanation

p(1)=1+a+b+2=0p(1) = 1 + a + b + 2 = 0, so a+b=3a + b = -3. p(2)=8+4a2b+2=0p(-2) = -8 + 4a - 2b + 2 = 0, so 4a2b=64a - 2b = 6, i.e., 2ab=32a - b = 3. Add: 3a=0a=03a = 0 \Rightarrow a = 0, b=3b = -3. Wait, a+b=3a + b = -3 with a=0a = 0 gives b=3b = -3. But choice says 1-1. Recompute: 2ab=32a - b = 3 with a=0a = 0 gives b=3b = -3. Hmm. Adjusting: actually with a=0a=0, the polynomial is x3+bx+2x^3 + bx + 2. With b=3b = -3: p(1)=13+2=0p(1) = 1 - 3 + 2 = 0 ✓; p(2)=8+6+2=0p(-2) = -8 + 6 + 2 = 0 ✓. So correct b=3b = -3.

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