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JAMB Mathematics 1984 Question 13

Question 13

Surds

Rationalize (5√7 − 7√5)/(√7 − √5)

  1. A.−2√35
  2. B.4√7 − 6√5
  3. C.−√35
  4. D.4√7 − 8√5
  5. E.√35.
Show the answer and explanation

Answer: C (−√35)

Explanation

Multiply top and bottom by √7 + √5. The bottom becomes 2 and the top 35 + 5√35 − 7√35 − 35 = −2√35, so the result is −√35.