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JAMB Mathematics 1991 Question 20

Question 20

Linear and Simultaneous Equations

Find the two values of y which satisfy the simultaneous equation 3x + y = 8, x2 + xy = 6

  1. A.−1 and 5
  2. B.−5 and 1
  3. C.1 and 5
  4. D.1 and 1
Show the answer and explanation

Answer: A (−1 and 5)

Explanation

From the first equation y = 8 − 3x. Substituting: x2 + 8x − 3x2 = 6, so x2 − 4x + 3 = 0 and x = 1 or 3. Then y = 5 or −1.