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JAMB 2011 · UTME · Q23

A binary operation ⊕\oplus on real numbers is defined by x⊕y=xy+x+yx \oplus y = xy + x + y. Find the value of 3⊕(−23)3 \oplus \left(-\frac23\right).

Worked solution (try it first)
  1. Put x=3x = 3 and y=−23y = -\frac23.
  2. The product is xy=3×(−23)=−2xy = 3 \times \left(-\frac23\right) = -2.
  3. So 3⊕(−23)=−2+3−233 \oplus \left(-\frac23\right) = -2 + 3 - \frac23.
  4. That is 1−23=131 - \frac23 = \frac13, option B.

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