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March 29, 2024, 08:28:46 am

Author Topic: Methods 1+2 Questions  (Read 1978 times)  Share 

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#1procrastinator

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Methods 1+2 Questions
« on: October 08, 2011, 10:45:39 am »
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Solve for x



Original equation is



I used the quadratic formula but and used the coefficients in the numerator and got close to the right answer, but I feel uneasy disregarding the denominator

What I got:

and


The book's solution is something like:

and


Thanks

pi

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Re: Methods 1+2 Questions
« Reply #1 on: October 08, 2011, 10:54:11 am »
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You're correct :)
« Last Edit: October 08, 2011, 11:00:55 am by Rohitpi »

#1procrastinator

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Re: Methods 1+2 Questions
« Reply #2 on: October 08, 2011, 11:00:51 am »
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Could you explain the bit about ignoring the denominators please? Why doesn't it affect the coefficients?

Also, my TI-89 gave the same answers as the book so I wasn't sure

pi

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Re: Methods 1+2 Questions
« Reply #3 on: October 08, 2011, 11:04:05 am »
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Could you explain the bit about ignoring the denominators please? Why doesn't it affect the coefficients?


What do you mean 'ignoring denominators'?

All the denominator of says (in terms of solutions) is that for all of


edit: pretty sure your answer is correct, wolfram alpha says so as well
« Last Edit: October 08, 2011, 11:08:35 am by Rohitpi »

#1procrastinator

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Re: Methods 1+2 Questions
« Reply #4 on: October 08, 2011, 11:32:55 am »
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That's all? I thought it meant divide by the function or something like that, thereby giving different coefficients

Oh ok, I might've entered something wrong...I'll  recheck

#1procrastinator

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Re: Methods 1+2 Questions
« Reply #5 on: October 19, 2011, 05:42:34 pm »
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ah yeah, I didn't notice the brackets

if you have an absolute value equation with absolute values on both sides, as in

|x+1| = 9|3-x|

In a video, the guy made both positive and then one negative and one positive. He didn't explain why, but from playing around with random equations, I'm guessing it's to find all cases - making both negative will always give positive right?

I'm not too comfortable with absolute values, is this covered in-depth in VCE math? or is it yr 8/9/10 math?



and when you have a complex fraction (i believe that's what i saw them being referred to as), such as [(1/3) + (1/9)]/3, why must you separate the fractions before flipping them?

i.e. you can't say it's equivalent to (1/3)/(3+9),

 i know you have to to get the right answer but i can't yet deduce the reason why

#1procrastinator

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Re: Methods 1+2 Questions
« Reply #6 on: October 28, 2011, 03:46:06 pm »
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This is from the extended response part of quadratics in the Essential book


Piece of wire (12cm) cut into two pieces. One used to form square shape, other a rectangular in which length is twice its width

If x is side length of square, write dimensions of rectangle nterms of x

I got (6-2x)/3 for width and (12-4x)/3 for length - answer given for width is (12-4x)/6

does it have to be that way or can you simplify it? and why would they not simplify it, is it just to show 12-4x?

dinosaur93

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Re: Methods 1+2 Questions
« Reply #7 on: October 28, 2011, 04:38:27 pm »
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Anyone have Unit 2 Methods Practise Exams?


Panicmode

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Re: Methods 1+2 Questions
« Reply #8 on: October 29, 2011, 02:14:52 pm »
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This is from the extended response part of quadratics in the Essential book


Piece of wire (12cm) cut into two pieces. One used to form square shape, other a rectangular in which length is twice its width

If x is side length of square, write dimensions of rectangle nterms of x

I got (6-2x)/3 for width and (12-4x)/3 for length - answer given for width is (12-4x)/6

does it have to be that way or can you simplify it? and why would they not simplify it, is it just to show 12-4x?

Your answer is correct, it's perfectly okay to simplify. I suspect the reason they left it unsimplified has got something to do finding area and making it easier.

ie. It's easier to say ; ((12-4x)^2)/(3x6) then it is to write ((6-2x)(12-4x))/(3x3)
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#1procrastinator

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Re: Methods 1+2 Questions
« Reply #9 on: October 31, 2011, 01:36:37 pm »
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^ thanks, just wanted to make sure

#1procrastinator

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Re: Methods 1+2 Questions
« Reply #10 on: November 02, 2011, 06:00:57 pm »
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how come using the finite differences method doesn't gives the wrong solutions when finding the equation to these plots

(0, 80) (2, 64) (4, 54) (6, 48) (8,44)

I got y = -1/3x^3 + 4x^2 - 19(2/3)x + 80 using the equations from the math quest book