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# C3 Help

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1. part iii)

Normally, we sub in x coordinate in f''(x) and if it >0 then it is minimum point and if it is <0 then it is maximum points.

If it is 0 then it could mean inflection. They are equation f''(x) = 0 to work out x and that gives you x coordinate of maximum point of f'(x). I don't understand it, that would get them the point where the inflection is if any, or it could be min, max??
2. (Original post by Bealzibub)

part iii)

Normally, we sub in x coordinate in f''(x) and if it >0 then it is minimum point and if it is <0 then it is maximum points.

If it is 0 then it could mean inflection. They are equation f''(x) = 0 to work out x and that gives you x coordinate of maximum point of f'(x). I don't understand it, that would get them the point where the inflection is if any, or it could be min, max??
You would set f''(x)<0

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3. (Original post by Bealzibub)

part iii)

Normally, we sub in x coordinate in f''(x) and if it >0 then it is minimum point and if it is <0 then it is maximum points.

If it is 0 then it could mean inflection. They are equation f''(x) = 0 to work out x and that gives you x coordinate of maximum point of f'(x). I don't understand it, that would get them the point where the inflection is if any, or it could be min, max??
No idea what you are asking.

To do part iii, set f''(x)=0 to find a maximum for the function f'(x).
4. (Original post by AlmostNotable)
No idea what you are asking.

To do part iii, set f''(x)=0 to find a maximum for the function f'(x).
What I'm confused about is, usually we find stationary points with f'(x) = 0

then that x value into f''(x) and if it is < 0 then it is maximum.

But you are saying f''(x) = 0? How can setting to 0 be maximum and < 0 is also maximum?
5. (Original post by Bealzibub)

part iii)

Normally, we sub in x coordinate in f''(x) and if it >0 then it is minimum point and if it is <0 then it is maximum points.

If it is 0 then it could mean inflection. They are equation f''(x) = 0 to work out x and that gives you x coordinate of maximum point of f'(x). I don't understand it, that would get them the point where the inflection is if any, or it could be min, max??
what paper is this?
6. (Original post by Bealzibub)
What I'm confused about is, usually we find stationary points with f'(x) = 0

then that x value into f''(x) and if it is < 0 then it is maximum.

But you are saying f''(x) = 0? How can setting to 0 be maximum and < 0 is also maximum?
We know that f ' (x) = 0 finds the stationary points for the function f (x).
Therefore f '' (x) = 0 finds the stationary points for the function f ' (x).
7. What is the paper so I can find this question?

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