Edexcel A2 C3 Mathematics 12th June 2015

Original post by Artfanatic

I think it always helps to draw it if you can. I am pretty sure you just complete the square then you know the min point is (2,7) on the graph so then it depends on the domain given, no?

Woah what? Do we complete the square to help us?

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Reply 1008

MasonPye

1

Are these IYGB papers more difficult than a standard paper?

Reply 1009

Original post by Artfanatic

I think it always helps to draw it if you can. I am pretty sure you just complete the square then you know the min point is (2,7) on the graph so then it depends on the domain given, no?

The answer is x>=7
So every time you get a question like this you complete the square?
and how does it depend on the domain?

Reply 1010

Original post by lam12

Woah what? Do we complete the square to help us?

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yeah I think so.. to find the range
I hate these questions :/ they are so confusing

Reply 1011

lam12

Original post by ridirahman

yeah I think so.. to find the range
I hate these questions :/ they are so confusing

Whattttt haha I've never done that, I need to learn this

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Reply 1012

Original post by lam12

Whattttt haha I've never done that, I need to learn this

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So how would you do the question? Is there another way or something?

Reply 1013

samb1234

13

Original post by ridirahman

So how would you do the question? Is there another way or something?

You could set the differential equal to 0 solve for x then plug that into the original equation

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Reply 1014

Original post by samb1234

You could set the differential equal to 0 solve for x then plug that into the original equation

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Ohh yeah okay thanks.

If you don't mind, can you explain how you would know whether to put <= or >= when finding the range/domain?

Reply 1015

samb1234

13

Original post by ridirahman

Ohh yeah okay thanks.

If you don't mind, can you explain how you would know whether to put <= or >= when finding the range/domain?

Either you can find d^2y/dX^2 to determine nature of the point or if there is just one turning point you could just plug one other number from the range/domain into the original equation and see if it gives a greater or lower answer

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Reply 1016

Nurishment

Original post by ridirahman

The function g is defined by g:x^2 – 4x + 11, x<=0. (b) Find the range of g.

As it says x<=0, would you substitute 0 into g which gives you 11 and that's the range?
Or do you complete the square of g and then find the range?

I always get confused don't know whether to substitute the range of x they give you to find the range of y or to complete the square/ factorise and then to find the range by drawing the diagram?

Wouldn't the range be g;x >= 11?
Completing the square just finds the minimum point at (2,7) in which the value of x is greater than 0 so the range wouldn't start from there?

Reply 1017

samb1234

13

Original post by Nurishment

Wouldn't the range be g;x >= 11?
Completing the square just finds the minimum point at (2,7) in which the value of x is greater than 0 so the range wouldn't start from there?

The range of a function describes what value f(x) can take. The minimum value of f(x) is 7 so the range is f(x)>=7

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Reply 1018

tajanamckenzie

someone help! ok so with the Rcos(x+a) for example and say you find out a and cos then it says work out the minimum value and the smallest possible value of x? Also for when it asks for the maximum and greatest possible value???? and what about for sine graph??? please help

Reply 1019

Nurishment