WAEC Mathematics 2015 Objective — Question 11

Question 11 of 50 from the West African Examinations Council (WAEC) Mathematics 2015 Objective paper, with the correct answer and a full explanation.

Adding 42 to a given positive number gives the same result as squaring the number. Find the number.

Explanation

Let the number be x: 42+x=x² → x²−x−42=0 → (x−7)(x+6)=0, so x=7 or x=−6. Since the number is positive, x=7.

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