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Year 12s: what will be the first way you research your future options? >>

Year 12s: what will be the first way you research your future options? >>

maths help

help please

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(edited 7 years ago)

OP

Original post by mervin101

help please

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Thread moved to maths. Please post in the maths forum for maths subject questions, thanks :smile:

:smile:

For this question, can you tell us what you've tried and post your working?

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Original post by mervin101

help please

The difference between

u_2

and

u_1

is the same as the difference between

u_3

and

u_2

OP

Original post by RDKGames

The difference between

u_2

and

u_1

is the same as the difference between

u_3

and

u_2

is that something i have to remember?

Study Forum Helper

Original post by mervin101

is that something i have to remember?

Of course. That's a fundamental property of an arithmetic sequence - the difference between each term is the same.

OP

Original post by RDKGames

Of course. That's a fundamental property of an arithmetic sequence - the difference between each term is the same.

so i wrote out this:
u3-u2 = u2-u1

so

(4k+1) - (2k+5) = (2k+5) - (k-2)

obviously i have to show k=11 so do I group the k terms and numbers?

Study Forum Helper

Original post by mervin101

so i wrote out this:
u3-u2 = u2-u1

so

(4k+1) - (2k+5) = (2k+5) - (k-2)

obviously i have to show k=11 so do I group the k terms and numbers?

Yes, just solve for k.

OP

Original post by RDKGames

Yes, just solve for k.

i have done A but how do i do b? is it differentiation? does f''(x) mean differentiate second principle

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Original post by mervin101

i have done A but how do i do b? is it differentiation? does f''(x) mean differentiate second principle

f''(x)

denotes the second derivative of

f(x)

- which can be equivalently called to be the first derivative of

f'(x)

. So yes just differentiate again.

OP

Original post by RDKGames

f''(x)

denotes the second derivative of

f(x)

- which can be equivalently called to be the first derivative of

f'(x)

. So yes just differentiate again.

thanks
i got f''(x) = 8+2x^-3

so that ^ was the second differential but what was the first? was it the function given? or 8x - x^-2 ?

Study Forum Helper

Original post by mervin101

thanks
i got f''(x) = 8+2x^-3

so that ^ was the second differential but what was the first? was it the function given? or 8x - x^-2 ?

The first derivative is given by

f'(x)

as I told you so yes it is

8x-x^{-2}

, but if you meant what the original function is, you need to integrate the first derivative function.

(edited 7 years ago)

OP

Original post by RDKGames

The first derivative is given by

f'(x)

as I told you so yes it is

8x-x^{-2}

, but if you meant what the original function is, you need to integrate the original function.

i understand now thank you

for c) to find f(x) do i integrate 8x-x^-2?

its 7 marks and im clueless

Study Forum Helper

Original post by mervin101

i understand now thank you

for c) to find f(x) do i integrate 8x-x^-2?

its 7 marks and im clueless

Yes..

OP

Original post by RDKGames

Yes..

but i dont understand the question
at first i thought "determine an equation of the curve" meant use the equation of a line (y-y1=m(x-x1)

y-y1=m(x-x1) is for finding the equation of a line. The question wants you to find the formula of a curve.
As y=f(x) you can the equation of the curve by integrating f'(x).

OP

Original post by TheFirstOrder

y-y1=m(x-x1) is for finding the equation of a line. The question wants you to find the formula of a curve.
As y=f(x) you can the equation of the curve by integrating f'(x).

Understood. So generally when I am asked to find the equation of a curve must I integrate?

Study Forum Helper

Original post by mervin101

Understood. So generally when I am asked to find the equation of a curve must I integrate?

Depends on the context.

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