AP Calculus BC Question 374: Answer and Explanation
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4. Which of the following is an equation of the tangent line to the curve described by the parametric equations x = t and y = t2 when t = 4 ?
- A. y = 8
- B. y = 2x + 8
- C. y = 8x - 16
- D. y = 8x + 16
Correct Answer: C
The correct answer is (C).
When t = 4, you have x = 4 and y = 16, and thus the point (4, 16) is on the curve. The slope of the tangent line is and when t = 4, . The equation of the tangent line is y - 16 = 8(x - 4) or y = 8x - 16.