WAEC 2013 Mathematics · Question 14

The graph of the relation y = x2 + 2x + k passes through the point (2, 0). Find the values of k

Options

A.zero
B.-2
C.-4
D.-8

Answer: D. -8

Explanation written with AI and checked against the answer key

Analyze the question: The curve y = x² + 2x + k passes through (2, 0). This means when x = 2, y = 0. We substitute these values to find k. Concept: If a point lies on a graph, its coordinates satisfy the equation of the graph. Solution: Substitute x = 2 and y = 0 into y = x² + 2x + k: 0 = (2)² + 2(2) + k 0 = 4 + 4 + k 0 = 8 + k k = -8 Check: With k = -8, y = x² + 2x - 8. At x = 2: 4 + 4 - 8 = 0 ✓ Answer: k = -8, which is option D. Tip: When a question says a graph "passes through a point (a, b)", just replace x with a and y with b in the equation, then solve for the unknown. Always do a quick check by substituting your answer back in.

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