VCE Methods Question Thread!

[KevinooBz]

hi easy question but

A car journey of 300 km lasts 4 h. Part of this journey is on a freeway at an average speed
of 90 km/h. The rest is on country roads at an average speed of 70 km/h.
Let T be the time (in hours) spent on the freeway.
a In terms of T, state the number of hours travelling on country roads.

T(total) = T(1) + T(2)
 Time=distance/speed
     4 = x/90 + 300-x/70 as the distance covered is unknown and the distance travelled on the country road would be 300 - whatever is travelled on the free way.
     4 = 7x/630 + 9(300-x)/630
        = 7x+2700-9x/630
2520= -2x+2700
      x=90
sub x=90 into t=(300-x)/70
                        =3 hours
                        =3T (I think)

[Smiley_]

Thanks

[darklight]

Question re: transformations

A transformation of y = 1/x^2 by a vertical translation of 2 units down, a horizontal translation of 5 units to the right and then dilation by a factor of 3 from the y-axis, is best represented as:

Shouldn't the answer be 1/(x/3 - 5)^2 - 2? My answer isn't one of the options, but the answer they give is y+2 = 1/(1/3(x-5))^2, i.e. the 1/3 is affecting "x-5" not just "x"...

[Daenerys Targaryen]

the book is correct
the needs to be taken out as a common factor

So that if you mutiply the number within the brackets by then it must = 5

[darklight]

the book is correct
the needs to be taken out as a common factor

So that if you mutiply the number within the brackets by then it must = 5

Yeah, but it doesn't equal to 5..it equals to -5/3 upon expanding.

[Daenerys Targaryen]

actullly.
forget what i said above

that still correct

if you let 1/3(x-5)=0
then x-5=0
x=5
meaning you're moving it right 5

[Jaswinder]

i think it should be



unless they do the dilations first :/

[Hancock]

Question re: transformations

A transformation of y = 1/x^2 by a vertical translation of 2 units down, a horizontal translation of 5 units to the right and then dilation by a factor of 3 from the y-axis, is best represented as:

Shouldn't the answer be 1/(x/3 - 5)^2 - 2? My answer isn't one of the options, but the answer they give is y+2 = 1/(1/3(x-5))^2, i.e. the 1/3 is affecting "x-5" not just "x"...

Since they have specified the order of transformations (translations first and then a dilation) the answer above me is correct (see the bolded 'then' in the quote). Usually, the order of transformations is Dr.T (doctor T). Dilations, Reflections and then Translations.

[darklight]

Since they have specified the order of transformations (translations first and then a dilation) the answer above me is correct (see the bolded 'then' in the quote). Usually, the order of transformations is Dr.T (doctor T). Dilations, Reflections and then Translations.

Awesome, so the worksheet is wrong! Thanks guys.

[abcdqdxD]

In the exam if you're asked to graph an equation, and you calculate the x/y intercepts, domain/range, shape incorrectly because you missed the negative sign in front of the equation, will you lose all 5 marks?

[zvezda]

In the exam if you're asked to graph an equation, and you calculate the x/y intercepts, domain/range, shape incorrectly because you missed the negative sign in front of the equation, will you lose all 5 marks?

yep, unfortunately. If I remember correctly, there are no consequentials in methods

[FlorianK]

yep, unfortunately. If I remember correctly, there are no consequentials in methods

There are consequentials. The marks are rewarded for specific things. Let's take the controversial conditional probability question. the marking scheme was:
1 mark for realising it is conditional probability
1 mark for choosing the right pairs (1,3) (2,2) (3,1)
1 mark for arithmetic working out

If you got 1 of them wrong you'd still be awarded 2 marks.

[Professor Polonsky]

You do get a mark for each feature of the graph (shape, intercepts etc.), so it is possible that you'd lose all marks if you got all features wrong. This assumes however that the equation of the graph was given to you. If you got the equation wrong as a result of a previous calculation, the marks will be awarded consequentially and you will get full marks (assuming, of course, you graphed correctly).

[h545]

Hi everyone,

I'm a bit confused with the order of transformations in this question:
The equation of the image of the graph of after a reflection in the y axis followed by a translation of 3 units in the positive direction of the x axis and 4 units in the negative direction of the y axis is: (multiple choice)

I got but the answer is supposed to be . Why does the reflection in the y axis affect the translation after it?

[Daenerys Targaryen]

Because if you take out - as a common factor so that which means it has been transposed 3 to the right. Other wise it becomes -(x+3) meaning 3 left