# Edexcel A2 C3 Mathematics 12th June 2015Watch

This discussion is closed.
3 years ago
#1201
(Original post by Ripper Phoenix)
square both sides and solve for x its easy
For mod equations, when can you NOT square both sides and what do you do then.
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3 years ago
#1202
(Original post by suyoof123)
For mod equations, when can you NOT square both sides and what do you do then.
let me show you give me a minute
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3 years ago
#1203
When you have to find out a in Rsin(x-a), do you use Sinx/Cosx or Cosx/Sinx ?
Cause most of the time I've needed to use Cosx/Sinx but it makes no sense to use it
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3 years ago
#1204
(Original post by Ripper Phoenix)
no its c3

also i have a strong feelin that we may be asked to draw modulus graphs like

y=IX+2I +2 or something like that lol

i'm paranoid
And how exactly would you draw y=|x+2| +2

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3 years ago
#1205
(Original post by suyoof123)
For mod equations, when can you NOT square both sides and what do you do then.

See this 😋

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3 years ago
#1206
(Original post by TheRaspberry)
I am really confused when solving these mod equations; for the 2nd solution, how do you know which side to put the minus on, because I am pretty sure there have been questions where it has been required for it to be put on alternate sides (e.g the minus on the mod equation side, and then on the non-mod side (not on the same question!!))

Sorry if this is confusing, but any help would be really appreciated. If anyone could just talk me through part b, to determine on which side you would put the minus, the question being from the June 2014 (R) paper that would also be much appreciated.

see the post above i posted the solution. Hope you understand
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3 years ago
#1207
(Original post by it's a me, mario)
And how exactly would you draw y=|x+2| +2

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that is exactly why i asked because i dont know.. edexcel forces my brain to think in weird ways
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3 years ago
#1208
(Original post by Ripper Phoenix)
that is exactly why i asked because i dont know.. edexcel forces my brain to think in weird ways
Draw graph of y = x, shift 2 units left, reflect negative values and shift 2 units up

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3 years ago
#1209
(Original post by Ripper Phoenix)
that is exactly why i asked because i dont know.. edexcel forces my brain to think in weird ways
I think i know actually

That graph is just built from the graph y=|x|

|x+2| would shift it left 2 units
+2 would shift it up two units

I think thats how you do it fam

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3 years ago
#1210
(Original post by aersh8)
Draw graph of y = x, shift 2 units left, reflect negative values and shift 2 units up

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(Original post by it's a me, mario)
I think i know actually

That graph is just built from the graph y=|x|

|x+2| would shift it left 2 units
+2 would shift it up two units

I think thats how you do it fam

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thought of it like that too thank you both
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3 years ago
#1211
(Original post by Ripper Phoenix)

See this 😋

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Thanks and you wouldnt put >/ (equals to ) or /< (equals to ) on this because if it were when equals or bigger/smaller than 0, then you would do that?.

Also originally I meant what happens if you have two mods on either side of the equation, would the squaring method still be viable.
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3 years ago
#1212
(Original post by it's a me, mario)
I think i know actually

That graph is just built from the graph y=|x|

|x+2| would shift it left 2 units
+2 would shift it up two units

I think thats how you do it fam

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Pretty sure you need to shift it left before you do the modulus of it

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1
3 years ago
#1213
(Original post by SeanFM)
Ah, so you've got values like 10, 12 in the second quadrant?

If so, it's possible that they specified a domain, or that they're not interested in the bits to the left of the y axis but you probably wouldn't lose marks unless they specified the domain.

I think it is possible, if it was +alpha and you had it in the form -alpha then alpha would be a negative value.
Ah ok thanks! do you mind helping me with https://07a69ccf283966549a9350d1a669...%20Edexcel.pdf 3c?
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3 years ago
#1214
https://07a69ccf283966549a9350d1a669...%20Edexcel.pdf

For 4b how do we know which value to use once we have done it with both a positive mod and negative mod?
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3 years ago
#1215
Does anyone have a list of formulas we need to know off the top of our head?

especially the trig functions
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3 years ago
#1216
(Original post by mat1996)
OMG, I can't believe i didn't see that. Thank you so much for your help but you know when I do it on the calculator it gives me -root3/9. Would examiners know this is equivalent or should i change it to the other answer (and how would I know this in the exam)
it is the same so no need to worry
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3 years ago
#1217
Whoops sorry everyone, think I scared everyone with that question on mod inequalities!
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3 years ago
#1218
Ah ok thanks! do you mind helping me with https://07a69ccf283966549a9350d1a669...%20Edexcel.pdf 3c?
Think about cos and the values it takes between 0 and 2pi, and try to spot the values that only come up once, and then see how you can apply that to find the correct answer.

https://07a69ccf283966549a9350d1a669...%20Edexcel.pdf

For 4b how do we know which value to use once we have done it with both a positive mod and negative mod?
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3 years ago
#1219
Just do the exam really slowly and check your answer after very question and then check everything again at the end. Just do that in a few past papers today and see if you come out any better?
Thanks for the advice I will make sure to do this
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3 years ago
#1220
(Original post by TheRaspberry)
Whoops sorry everyone, think I scared everyone with that question on mod inequalities!
not really
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