Question in math adv test that cost me my grade since idk how to do it (1 Viewer)

[C2H6O]

heres what I did, idk if this is any easier than what your teacher said but it’s the most straightforward approach. Start by solving simultaneous treating k as a constant. Get equation for x by substitution, rearrange for x to get a fraction with a quadratic in denominator like you said. substitute x into y and do the same (the denominator is basically the same quadratic so this doesn’t change anything). No solutions for x, y when quadratic = 0 at k=4/3 or k=-2

 

[killer queen]

@cheesynooby i got k=2/-2 but thats only k=-2 is ONE of the solutions + i didnt get a quadratic equation so i did it wrong

can we see your working maybe?

 

[C2H6O]

@cheesynooby genius idea, I’ve tried it and got the same answers. However I had to eliminate k=-2 as a solution cause that would make the lines have the same gradient and same y intercept thus being the same line. I’m guessing we had to sub back in using the other method or something to eliminate k=-2?

 

[jane1820]

can we see your working maybe?

 

[jane1820]

teachers working out btw

 

[killer queen]

View attachment 47272
teachers working out btw

ngl I like @cheesynooby's method better (as shown by @C2H6O, I was gonna show my working but was too late oops)

 

[C2H6O]

View attachment 47272
teachers working out btw

hmm ok well ive verified with desmos and k=-2 indeed gives the same lines, so i think it should have been eliminated as a solution. if this is true then maybe you can get the question omitted?

 

[cheesynooby]

hmm ok well ive verified with desmos and k=-2 indeed gives the same lines, so i think it should have been eliminated as a solution. if this is true then maybe you can get the question omitted?

yeah i think k = –2 is wrong

 

[C2H6O]

ok nup i double checked idk whats going on here but maybe k=-2 is actually correct (i subbed back into the 2 linear eqs)

 

[jane1820]

hmm ok well ive verified with desmos and k=-2 indeed gives the same lines, so i think it should have been eliminated as a solution. if this is true then maybe you can get the question omitted?

Tmr is last day of school n we have cross country (its the whole day) and my teacher wont be bothered
also she made it VERY clear that if we do walk out of class on wednesday with our test in hand thats it she’s 100% not changing anything anymore (mark addition, reviewing, eliminating questions etc) so highly doubt it

 

[jane1820]

Anyways idk i feel like that question is relatively hard for an advanced question (what do you guys think?)
also she kept yapping abt how the hsc is gonna be so much harder n if we cant solve questions like this from now we should drop

 

[C2H6O]

ok nup i double checked idk whats going on here but maybe k=-2 is actually correct (i subbed back into the 2 linear eqs)

WAIT NO I MADE A TYPO IN DESMOS k=-2 IS NOT A SOLUTION

 

[cristal]

on the other hand I uh made a complete muck up of this ^^
yeah I eliminated the k-
I mean normally they have to give a hard q to challenge students like the adv question my school got. Also mucked that one up
but easier than this one I'd say

 

[C2H6O]

Anyways idk i feel like that question is relatively hard for an advanced question (what do you guys think?)
also she kept yapping abt how the hsc is gonna be so much harder n if we cant solve questions like this from now we should drop

Yeah its definitely on the harder side of the spectrum for adv due to the complexity, but she is somewhat right that you should get good at solving these more easily or like being able to know the steps for these types of questions. not to scare you tho i dont really like it when teachers scare us into dropping you should only drop if you are clearly struggling hard or hate the subject

 

[cheesynooby]

View attachment 47271

i think u forgot the - on the 4th line woops

 

[killer queen]

Anyways idk i feel like that question is relatively hard for an advanced question (what do you guys think?)
also she kept yapping abt how the hsc is gonna be so much harder n if we cant solve questions like this from now we should drop

I am by no means the expert here but in my personal opinion, this would probably be a harder question in the HSC unless there were significant like lead in questions before (like multiple parts), this seems like the sort of thing designed to test your thinking instead of your math ability if that makes any sense
I doubt it would be like the hardest but it'll probably be in the latter half of the paper? Luckily this is the kind of question where it's like if you've seen it once, ingrain it in your brain and if you ever come across it again you'll have an inkling of how to approach it later

 

[jane1820]

The teacher said its our fault if we didnt know how to solve it bc it means (and i quote) ‘you cant apply your previous knowledge to new concepts’ which in one way or another i agree

 

[tywebb]

it’s much quicker to use coefficient matrix

 

[cheesynooby]

it’s much quicker to use coefficient matrix

that's not in the syllabus lol

 

[m_avi]

it’s much quicker to use coefficient matrix

Never seen that before :0