Should I get aleast one mark? (1 Viewer)

[M@ster P]

Hi guys I got my maths exam test back today, and I saw for one of the questions that is worth 2 marks, i got 0.

The question is integrate [ (2x + 3)^3 / 4 ], now the obvious thing is to add one to the power and times the denominator by the derviative of the numerator, however instead I expanded it out then I integrated each term individually, don't ask me why I just did.

Should I atleast get one mark, because technically they are both correct answers, except one answer is in a more factorised form and the other answer is the expanded form of that factorised form. Simply the answer can be expressed in different forms.

So should I atleast get one mark for that question? or even 2?

 

[tommykins]

if your answer factorises to the correct integral, you should get full marks.

 

[dp624]

I agree, full marks

 

[M@ster P]

Serious I was hoping for one, and the answer is exactly the same just expressed in different forms.

Ok I will complain

further opinions are welcome

 

[dp624]

can you scan for us, just to make sure?

 

[M@ster P]

I don't have a scanner but i will type it up, so wait...

 

[lyounamu]

Hi guys I got my maths exam test back today, and I saw for one of the questions that is worth 2 marks, i got 0.

The question is integrate [ (2x + 3)^3 / 4 ], now the obvious thing is to add one to the power and times the denominator by the derviative of the numerator, however instead I expanded it out then I integrated each term individually, don't ask me why I just did.

Should I atleast get one mark, because technically they are both correct answers, except one answer is in a more factorised form and the other answer is the expanded form of that factorised form. Simply the answer can be expressed in different forms.

So should I atleast get one mark for that question? or even 2?

Answer should be:
1/4 . x . (x+3) . (2x(x+3) + 9)

 

[cutemouse]

Did you expand it out correctly?

If so, you should get full marks. But it also depends on how everyone else was marked.

 

[M@ster P]

ok the question was actually integrate/find the primitive function of (2x + 3)^3.......... my bad

Fast method, answer equals (2x + 4)^4 / 8 + C

My long method that got 0/2 marks.

(2x + 3)^3
= (2x + 3)^2 (2x + 3)
=................
=8x^3 + 36x^2 + 54x + 27

integrating

= 2x^4 + 12x^3 + 27x^2 + 27x + C

I just expanded the (2x + 4)^4 / 8 + c out and got 2x^4 + 12x^3 + 27x^2 + 27x + C

also found C was 81

 

[lyounamu]

ok the question was actually integrate/find the primitive function of (2x + 3)^3.

Fast method, answer equals (2x + 4)^4 / 8 + C

My long method that got 0/2 marks.

(2x + 3)^3
= (2x + 3)^2 (2x + 3)
=................
=8x^3 + 36x^2 + 54x + 27

integrating

= 2x^4 + 12x^3 + 27x^2 + 27x + C

I just expanded the (2x + 4)^4 / 8 + c out and got 2x^4 + 12x^3 + 27x^2 + 27x + C

you mean 3?

What is it? is it (2x+4) or (2x+3)?

 

[lyounamu]

The answer to the "quick" method is:

(2x+3)^4/32 + c

edit: just realisd that you changed the question

the answer to the "quick" method is:

(2x+3)^4/8 + c as you mentioned

but using the long method:

it is

(2x+3)^3 = 8x^3 + 36x^2 + 54x + 27

integrate that, you get: 2x^4 + 12x^3 + 27x^2 + 27x + c

 

[M@ster P]

arrgg sorry its a 3 not a 4

 

[M@ster P]

Thanks guys, I will complain

 

[dp624]

Thanks guys, I will complain

keep us posted =P and good luck

 

[M@ster P]

keep us posted =P and good luck

Cheers, I don't think i need it cause everyone here agrees that I should get 2 marks, plus I will show the proof, however this teacher is known to be tight in her marking so I still might get 0 , nonetheless i will try.

I will post next monday whether i got the 2marks or not.

Adios!!!

 

[minijumbuk]

If it was 3u, you'd probably lose 1 mark, since you didn't factorise your final answer.

However in 2u, you deserve your full 2 marks.

 

[Trebla]

Don't get your hopes up too high. Some teachers can get very anal, and they might accuse you of writing it in when you got them back, not in the exam. That happened to me in a Chemistry trial exam once, where I handed in the paper for a recheck because the marker skipped one of the questions and my answer was correct.

When I got it back, I was not given the mark because they accused me of writing it when I got it back...so I lost a mark thanks a stupid marker who was blind enough to miss my answer and skip marking the question....not to mention being falsely accused of cheating :angry:

 

[Zephyrio]

Don't get your hopes up too high. Some teachers can get very anal, and they might accuse you of writing it in when you got them back, not in the exam. That happened to me in a Chemistry trial exam once, where I handed in the paper for a recheck because they skipped one of the questions and my answer was correct.

When I got it back, I was not given the mark because they accused me of writing it when I got it back...so I lost a mark thanks a stupid marker who was blind enough to miss my answer and skip marking the question....not to mention being falsely accused of cheating :angry:

Our science staff...

I was comparing ours to Ruse and found Ruse to be so much more dedicated to the education of their kids. For one, they did not recycle past papers, and thus they could just give back test papers so kids could download them from the school server along with answers. Not to mention their topic/trials/half yearly tests to be quite similar to HSC-standard questions.

 

[dp624]

Our science staff...

I was comparing ours to Ruse and found Ruse to be so much more dedicated to the education of their kids. For one, they did not recycle past papers, and thus they could just give back test papers so kids could download them from the school server along with answers. Not to mention their topic/trials/half yearly tests to be quite similar to HSC-standard questions.

Oh you have NOT seen our physics staff. THey are so FULL of epic fail.
CHem is good however

 

[Trebla]

Oh you have NOT seen our physics staff. THey are so FULL of epic fail.
CHem is good however

Hmmm.....Mr Kowalski??? He originally came from Sefton....