Not sure about these answers

I was doing a Core 3 Past Paper (AQA, June 2014) but wasn't entirely sure about how many marks I would get for some questions:

On question 2)a, it says dy/dx = -2 x (1/(2e-x))

I put dy/dx = -2 / 2e-x. Is this full marks?

Likewise for question 3)a:

The markscheme says 5/2 x 2x(x^2+1)^3/2

I put 5x(x^2+1)^3/2

For 3)b, the question says to find the x coordinates of the stationary points. I found them correctly, but I also found the y coordinates. Do I drop a mark for this?

For question 4)c)i, the markscheme says the stretch is scale factor 1/2 // x axis

Is stretch, scale factor 1/2 in the x direction the right thing?

For 6)a, the markscheme puts the constant of integration as a capital C

I put mine as a lower case c. Do I drop the final mark?

Thanks for all your help :smile:

(edited 8 years ago)

Reply 1

Zacken

22

Original post by MathsALevel123

I was doing a Core 3 Past Paper (AQA, June 2014) but wasn't entirely sure about how many marks I would get for some questions:

On question 2)a, it says dy/dx = -2 x (1/(2e-x))

I put dy/dx = -2 / 2e-x. Is this full marks?

Assuming the -2 x (...) is multiplication, you would get full marks.

Original post by MathsALevel123

Likewise for question 3)a:

The markscheme says 5/2 x 2x(x^2+1)^3/2

I put 5x(x^2+1)^3/2

Assuming 5/2 x 2 x (x^2+1)^(3/2) (bolded is multiplication) then yes, full marks.

Original post by MathsALevel123

For 3)b, the question says to find the x coordinates of the stationary points. I found them correctly, but I also found the y coordinates. Do I drop a mark for this?

No. Full marks.

Original post by MathsALevel123

For question 4)c)i, the markscheme says the stretch is scale factor 1/2 // x axis

Is stretch, scale factor 1/2 in the x direction the right thing?

You may lose a mark here, x direction is a bit ambigous, I would stick with stretch parallel to the x axis, that's what the // means parallel.

Original post by MathsALevel123

For 6)a, the markscheme puts the constant of integration as a capital C

I put mine as a lower case c. Do I drop the final mark?
No.

Reply 2

MathsALevel123

OP

1

Original post by Zacken

Assuming the -2 x (...) is multiplication, you would get full marks.

Assuming 5/2 x 2 x (x^2+1)^(3/2) (bolded is multiplication) then yes, full marks.

It is 5/2 times 2x (x^2+1)^3/2 and I put 5x(x^2+1)^3/2

No. Full marks.

You may lose a mark here, x direction is a bit ambigous, I would stick with stretch parallel to the x axis, that's what the // means parallel.

Oh. I always used to do parallel to the x axis but then I changed it for some reason...

What's the difference between the 2?

No.

Reply 3

Zacken

22

Original post by MathsALevel123

It is 5/2 times 2x (x^2+1)^3/2 and I put 5x(x^2+1)^3/2

No. Full marks.

You may lose a mark here, x direction is a bit ambigous, I would stick with stretch parallel to the x axis, that's what the // means parallel.

Oh. I always used to do parallel to the x axis but then I changed it for some reason...

What's the difference between the 2?

No.

Well, you could mean a stretch perpendicular to the x-axis, you need to state that it's parallel.

Also, yes, your 5/2 thing is correct.

Reply 4

MathsALevel123

OP

1

Original post by Zacken

Well, you could mean a stretch perpendicular to the x-axis, you need to state that it's parallel.

Also, yes, your 5/2 thing is correct.

Ok. Thanks for all your help :smile:

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