Question 23
Linear and Simultaneous EquationsFind two values of y which satisfy the simultaneous equations x + y = 5, x2 − 2y2 = 1
- A.12, −2
- B.−12, 12
- C.−12, 2
- D.2, −2
Show the answer and explanation
Answer: C (−12, 2)
Explanation
Put x = 5 − y into the second equation: (5 − y)² − 2y² = 1, which becomes y² + 10y − 24 = 0. So (y + 12)(y − 2) = 0 and y = −12 or 2.