Solution

ID: past-exam-of-the-mathematics-course-of-the-year-1-of-the-natural-sciences-course-of-the-university-of-cambridge/2012/paper-1/2/solution

The derivative of the parabola is , giving tangent line slope at . A normal line to a plane curve has the negative reciprocal slope, since its direction is orthogonal to a tangent vector. Hence
The point satisfies the equation, and the product of the two slopes is .

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