For those 1 marker type questions in binomial expansions, where they ask for the set of values of x for which your expansion is valid, what if you're adding two different expansions together?

What would the set of values be?

Reply 1306

somevirtualguy

2

Original post by 1 8 13 20 42

What would you do if that original integral was just any old variable?

Spoiler

Ignore me I've just done it, it feels like really dodgy maths haha but it makes sense thanks for the help :smile:

Reply 1307

anonwinner

19

Guys is there any 1/2 marker worded answers we should know for C4? For example in the C3 paper there was that one about it being a many to one function.

Another example would be in C4 when you have to say if the trapezium rule has overestimated or underestimated the area, and you say whether the trapezia lie above or below the curve

Reply 1308

math42

20

Original post by nbofni

For those 1 marker type questions in binomial expansions, where they ask for the set of values of x for which your expansion is valid, what if you're adding two different expansions together?

What would the set of values be?

Whichever restriction is tighter
For instance if one is |x| < 8/9 and another is |x| < 1/4, both must hold, but if |x| < 1/4, then |x| < 8/9 anyway

Reply 1309

anndz3007

2

Original post by anonwinner

Guys is there any 1/2 marker worded answers we should know for C4? For example in the C3 paper there was that one about it being a many to one function.

Another example would be in C4 when you have to say if the trapezium rule has overestimated or underestimated the area, and you say whether the trapezia lie above or below the curve

think thats all you need

Reply 1310

anndz3007

2

anyone has any hard set of integration questions, that the topic that i think Edexcel will try to ''ra pe'' us with

Reply 1311

joe1545

14

Original post by anonwinner

Guys is there any 1/2 marker worded answers we should know for C4? For example in the C3 paper there was that one about it being a many to one function.

Another example would be in C4 when you have to say if the trapezium rule has overestimated or underestimated the area, and you say whether the trapezia lie above or below the curve

The other would be in differential equations, where you have to say what certain variables represent.
Or I was doing a Solomon paper today and you had to comment on the sustainability of a mathematical.
model
Wouldn't get two worked up on 1/2 markers though as it's completely dependent on the question.

Reply 1312

Leking9

11

Oh gosh, how am I going to get 90, given the amount of silly errors I make

Reply 1313

jubilant_joej

1

How likely is it we'll be asked to form a differential equation from some information? And any tips on doing this?

Reply 1314

username1200599

12

Original post by a.a.k

I dont know what i am doing but i think u can implicit differentiate 3^xy.

Am i right/wrong?

Posted from TSR Mobile

I had a go, not sure if it's right. Your working doesn't seem to have any implicit differentiation in it?
Apologies for poor lighting. Why are you trying to implicitly differentiate that?

EDIT: My bad just realised I forgot to multiply out the bracket fully.

(edited 8 years ago)

1434316838892-1912253636.jpg176.8KB

Reply 1315

Gilo98

14

Original post by jubilant_joej

How likely is it we'll be asked to form a differential equation from some information? And any tips on doing this?

kind of likely. the Qs are very similar though. give you a formula. give the rate of change of 1 of the variables in formula and want you to find the rate of change of the other variable in the formula at some value. always end up differentiating the formula and diving this derivative by the rate of change they give you before subbing in the value they want the rate of change at.

Reply 1316

jubilant_joej

1

Original post by Gilo98

kind of likely. the Qs are very similar though. give you a formula. give the rate of change of 1 of the variables in formula and want you to find the rate of change of the other variable in the formula at some value. always end up differentiating the formula and diving this derivative by the rate of change they give you before subbing in the value they want the rate of change at.

Sorry, I didn't mean related rates of change, I meant whats the likelihood of them giving us some information:
e.g. 'A bath is filled with hot water which is allowed to cool. The temperature of the water is theta degrees after cooling for t minutes and the temperature of the room is assumed to remain constant at 20 degrees.
Given that the rate at which the temperature of the water decreases is proportional to the difference in temperature between the water and the room.
Write down a differential equation connecting theta and t

Reply 1317

username1200599

12

Original post by a.a.k

I dont know what i am doing but i think u can implicit differentiate 3^xy.

Am i right/wrong?

Posted from TSR Mobile

Original post by veggienator

That'll be great :yy:

Original post by TheAnnabelle

Hmm....I'm not sure...I'll see if I can ask a teacher tomorrow and get back to you guys

Here your guys go:

The result is the bit in the middle surrounded by scribbles, and ignore the equating to 0. I just do that without thinking :P

Also if you want to check your answer you can use Wolfram Alpha: http://www.wolframalpha.com/input/?i=differentiate+3%5E%28xy%29+wrt+x

(edited 8 years ago)

Reply 1318

Gilo98

14

Original post by jubilant_joej

Sorry, I didn't mean related rates of change, I meant whats the likelihood of them giving us some information:
e.g. 'A bath is filled with hot water which is allowed to cool. The temperature of the water is theta degrees after cooling for t minutes and the temperature of the room is assumed to remain constant at 20 degrees.
Given that the rate at which the temperature of the water decreases is proportional to the difference in temperature between the water and the room.
Write down a differential equation connecting theta and t

ohhh sorry, my bad - i think i read in the spec that we will not be expected to form D.E's but I'm not entirely sure. Those examples such as yours above however should be fairly straightforward.

Reply 1319

username1200599

12

Original post by jubilant_joej

Sorry, I didn't mean related rates of change, I meant whats the likelihood of them giving us some information:
e.g. 'A bath is filled with hot water which is allowed to cool. The temperature of the water is theta degrees after cooling for t minutes and the temperature of the room is assumed to remain constant at 20 degrees.
Given that the rate at which the temperature of the water decreases is proportional to the difference in temperature between the water and the room.
Write down a differential equation connecting theta and t

You might be asked to? I don't know, I've been doing it in the Solomon papers. I know it's definitely a possibility in FP2 but I don't know for C4. I would just say best to have a little practice just in case though lol.

Edexcel A2 C4 Mathematics June 2015 - Official Thread

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