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A curve has equation $y = f(x)$ The curve has a point of inflection at $x = 7$ It is given that $f'(7) = a$ and $f''(7) = b$, where $a$ and $b$ are real numbers - AQA - A-Level Maths Mechanics - Question 2 - 2021 - Paper 2

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A-curve-has-equation-$y-=-f(x)$-The-curve-has-a-point-of-inflection-at-$x-=-7$-It-is-given-that-$f'(7)-=-a$-and-$f''(7)-=-b$,-where-$a$-and-$b$-are-real-numbers-AQA-A-Level Maths Mechanics-Question 2-2021-Paper 2.png

A curve has equation $y = f(x)$ The curve has a point of inflection at $x = 7$ It is given that $f'(7) = a$ and $f''(7) = b$, where $a$ and $b$ are real numbers. Ide... show full transcript

Worked Solution & Example Answer:A curve has equation $y = f(x)$ The curve has a point of inflection at $x = 7$ It is given that $f'(7) = a$ and $f''(7) = b$, where $a$ and $b$ are real numbers - AQA - A-Level Maths Mechanics - Question 2 - 2021 - Paper 2

Step 1

Identify which one of the statements below must be true.

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Answer

To determine whether f(7)f'(7) must equal zero, we analyze the information given:

A point of inflection is where the concavity of a function changes, which implies that the second derivative at that point, f(7)f''(7), must equal zero. However, there is no direct requirement for the first derivative at that point, f(7)f'(7), leading to four possibilities:

  • It could be zero,
  • It could be positive,
  • It could be negative, or
  • It could be undefined.

Given that no specific condition is stated for f(7)f'(7) other than what is necessary for a point of inflection, we conclude that:

Therefore, the correct answer must be: f(7)=0f'(7) = 0

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