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AP®︎/College Calculus AB

Course: AP®︎/College Calculus AB>Unit 9

Lesson 1: AP Calculus AB 2017 free response

2017 AP Calculus AB/BC 4a

Potato problem from 2017 AP exam (Question 4). Finding and using the equation of a tangent line to approximate solution to differential equation.

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• Using the tangent line at t=0 to approximate the temperature at t=3 is kind of far fetched, or am I missing something here?
• yes, it is an underestimate. This is addressed in the next video.
• Why is this problem considered infamous?
• It's really not that hard; people likely just forgot separation of variables and differential equations. It's infamous because not a lot of people got it right (all problems seem a lot harder in the exam room) and a lot of people made memes about the problem, because "baked potato at 91 degrees" is a lot more memorable than other problems like "area of polar curve".
• Is y the same variable as H?
• Yes, you could think of it in that way. Both H and y are functions respect to time. They are just different notations.
• Are there any videos for the other 2017 free response questions?
• How did he get the idea of multiplying dH/dt by t? ()
• Khan is using the formula for the equation of a line y=mx+b, he is substituting dH/dt for m and 91 for b (since that is the initial temperature for the potato)
• What should I practice specifically do this kind of problem on my own (for parts A-C)?
• Those questions rely on your knowledge of Differential Equations. So, practice that.
• I used differential equations to solve this and it is about 57.23 degrees C, is this correct?
• You shouldn't, they've asked you to approximate it using the equation of the tangent.