VCE Methods Question Thread!

[exit]

hi, someone help me get the calc to do this:

solve(normCDf(500,510,2,x)=0.95,x)

It just spouts out the equation in a different format... pretty sure I could do this before.

Using the Classpad 400, if you are using a texas let me know if you can do this.

Thanks!!

[keltingmeith]

hi, someone help me get the calc to do this:

solve(normCDf(500,510,2,x)=0.95,x)

It just spouts out the equation in a different format... pretty sure I could do this before.

Using the Classpad 400, if you are using a texas let me know if you can do this.

Thanks!!

I think you want the invnorm function?

[Biology24123]

A car travels half the distance of a journey at an average fo 80 km/h and half at x km/h. Define a function,S, which the average speed for the total journey as a function of x.

[Biology24123]

S(x)=(x+80)/2

Answers say 160x/(x+80) so no

[geminii]

Hey everyone, I have two questions from my textbook that I don't understand.

1. The simultaneous equations x + y = 6 and 2x + 2y = 12 have infinitely many solutions. Describe these solutions through the use of a parameter.

[I don't know what a parameter is... or how to solve this. I'm still in the holiday mood]

2. The family of lines y = mx + 6 with varying gradient m all pass through the point (0,6).
a) For what values of m does the line y = mx + 6 not intersect the line y = 4x - 5?
b) For what values of m does the line y = mx + 6 intersect the line y = 4x - 5?
c) If the line y = mx + 6 intersects the line y = 4x = 5 at the point (5,15), find the value of m.

[I don't understand the method that needs to be used to solve this one]


Worked solutions would be amazing!!! Thanks so much

[keltingmeith]

Hey everyone, I have two questions from my textbook that I don't understand.

1. The simultaneous equations x + y = 6 and 2x + 2y = 12 have infinitely many solutions. Describe these solutions through the use of a parameter.

[I don't know what a parameter is... or how to solve this. I'm still in the holiday mood]

Welp, you can't solve it because there is no singular solution. Only an infinite amount, and they all lie along the line x+y=6.

Asking them to "describe the solutions through a parameter" is super weird and I don't think you'll ever get asked that in an exam. However, you would use a parameter like so:

x=t
y=6-t

where t is the parameter. Basically, if you sub in a bunch of different values for t, you'll get different values for x and y. If you map these points on a Cartesian plane, you'll get the equation x+y=6. It does not come up in methods, so I'd ignore it if you're unsure.

2. The family of lines y = mx + 6 with varying gradient m all pass through the point (0,6).
a) For what values of m does the line y = mx + 6 not intersect the line y = 4x - 5?
b) For what values of m does the line y = mx + 6 intersect the line y = 4x - 5?
c) If the line y = mx + 6 intersects the line y = 4x = 5 at the point (5,15), find the value of m.

[I don't understand the method that needs to be used to solve this one]

For these questions, I suggest drawing a bunch of lines! What gradient would a line need to not touch the graph y=4x-5 at any point? (you might find your CAS useful here) From that, what possible gradients would then cause a single intersection? And part c is just using the fact that the point (5,15) exists on both lines to find m.

[qazser]

A car travels half the distance of a journey at an average at 80 km/h and half at x km/h. Define a function,S, which the average speed for the total journey as a function of x.

Yahoo answers:
Let the distance of journey = L
time taken during L/2 distance of traveling at a speed of 80 = t1 = distance/speed = L/2* 1/80 = L/160
time taken during L/2 distance of traveling at a speed of x= t2 = = L /(2x)
average speed = S = distance / total time = L / (t1 +t2) = L / (L/160 + L / 2x) = 160x/(x+80)

[she0071]

Hi! I'm not very sure on this multiple choice question:
The area of a triangle formed by the x-axis, the y-axis and the graph of the line with the equation, 3y=6-2x is:
A 3
B 4
C 5
D 6
E 8

Thankyou!

[/quote]

[Syndicate]

Hi! I'm not very sure on this multiple choice question:
The area of a triangle formed by the x-axis, the y-axis and the graph of the line with the equation, 3y=6-2x is:
A 3
B 4
C 5
D 6
E 8



Thankyou!

let x = 0 and you would get y = 2 (0,2)

let y= 0, and you would get x = -3 (3,0)

2 is the height and 3 is the base
1/2 x bh
1/2 x (3)(2)
1/2 x 6 = 3

Therefore, the correct answer is A

[exit]

I have a track record of being terrible with the calc (classpad 400)...its not too late to get a Ti CX if required, however  already starting yr 12 MM.... 2 years exp with cp400 however i suspect this calc might be trash by seemingly treating x and y differently from other variables in everything

Anything would help IMMENSELY:

1. How to solve something like this: t=x/(x-a) on calc without having to change t to a y?
2.How to solve x and y in terms of a and b for these 2 equations on calc :
   2ax+2by=3
   3ax-2by=7
3.How to convert partial fractions to 'mixed' form (1 number, 1 fraction)
4. How to solve simultaneous equations in general in terms of other variables/letters.

If i try [solve(x^2-4x=t,x)]

I get incorrect argument even though it is exactly what you're supposed to do... even though all the variables are cleared.

EDIT: The problem was solved with the command: [Clear_a_z]. The monkeys at casiobroke the 'Clear All Variables' button..should have got a tinspire earlier on and stuck with it...

Still, I need help with the partial fractions 

Danke

[exit]

Tip: make sure the variables you type come from the VAR tab.
1.  Enter t=x/(x-a), highlight, interactive > advanced > solve > ok
2. 2D > symbol that inserts a curly bracket with 3 boxes (two boxes and one box separated by a line) > enter first equation into first box > enter second equation into box below that > enter x,y into last box
3. Enter fraction > highlight > interactive > transformation > propFrac (combine reverses this)
4. See 2. Instead of x,y enter the letters you want to solve for.

Thanks for the elaborate reply, turns out the "clear all variables' button on the calc didn't do anything so I had to type in the command. Very disturbing how the button doesn't work properly.

[exit]

Is there a physical button? (I have the older version and I usually just go edit > clear all variables)

Nope, the button is under Edit (top of screen) > Clear All Variables

but the button didn't do anything so I had to go Keyboard > Catalog > and find Clear_a_z which solved the problem

[exit]

hi, someone help me get the calc to do this:

solve(normCDf(500,510,2,x)=0.95,x)

It just spouts out the equation in a different format... pretty sure I could do this before.

Using the Classpad 400, if you are using a texas let me know if you can do this.

Thanks!!

^ still need help with this thanks. I'm trying to find the mean which both CDf functions don't do..

Both invCDf and NormCDf don't solve for mean

[she0071]

let x = 0 and you would get y = 2 (0,2)

let y= 0, and you would get x = -3 (3,0)

2 is the height and 3 is the base
1/2 x bh
1/2 x (3)(2)
1/2 x 6 = 3

Therefore, the correct answer is A

Thankyou!

So for those of you keen to indulge yourself in the wonders of methods 3/4 throughout the holiday coz u have nothing better to do, post away your questions in this thread. Everyone can discuss and benefit from this, i'll personally try to answer all the questions that's posted too

the more discussion the better, once a question is posted feel free to post all kinds of solutions, talk about other things related to the question and feel free to go on mathematically related tangents, that's how one improves at maths!

[Sarah P]

Can someone help me with this question please?It is;

If  2x^3 - 5x^2 + 5x- 5= a(x-1)^3 + b(x-1)^2 + c(x-1) + d, find the values of a,b,c,d and hence express 2x^3 - 5x^2 + 5x - 5 in the form a(x-1)^3 + b(x-1)^2 + c(x-1) + d.

the answer is a=2, b=1, c=1 and d=-3, but I have no idea how they managed to get it. Any help is much appreciated