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anyone need help for maths?

shwansalah

Exam tommorow and i'll be glad to help with your revision, so fire away.

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Reply 1

chazer154

Concerning graphical transformations...what's the difference between f(2x) and 2f(x) ?????

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Reply 2

aadil10

Original post by chazer154

Concerning graphical transformations...what's the difference between f(2x) and 2f(x) ?????

Posted from TSR Mobile

2f(x) stretches the graph vertically by twice as much.

f(2x) stretches (or squashes) it by 1/2 horizontally

(edited 8 years ago)

Reply 3

shwansalah

Original post by chazer154

Concerning graphical transformations...what's the difference between f(2x) and 2f(x) ?????

Posted from TSR Mobile

2f(x) stretches the function twice vertically and f(2x) makes the function smaller horizontally by 0.5

Reply 4

miageogiaxxxx

i need help with probability

Reply 5

Emilythorb

I don't understand how to factorise fully - I can only do simple and I can't prove algebraically

Reply 6

aadil10

Original post by miageogiaxxxx

i need help with probability

What specifically?

want an example?

Reply 7

shwansalah

Original post by Emilythorb

I don't understand how to factorise fully - I can only do simple and I can't prove algebraically

ok can you factorise 2x squared + 7x + 6?

Reply 8

miageogiaxxxx

Original post by aadil10

What specifically?

want an example?

just in general do not understand :frown:

like it completely confuseses me
for example: 4 girls , 6 boys in one class, whats the probability teacher choses two boys if he selects two students at random

Reply 9

Emilythorb

Original post by shwansalah

ok can you factorise 2x squared + 7x + 6?

Hm I would probably say x ( x + 7 And then I'd be stuck

Reply 10

aadil10

Original post by miageogiaxxxx

just in general do not understand :frown:

like it completely confuseses me
for example: 4 girls , 6 boys in one class, whats the probability teacher choses two boys if he selects two students at random

Okay so first thing about the probabilities of each one just once.

Add them all together first so 4+6=10 students in the class

this means: 4/10 girls 6/10 boys which you can simplify to 2/5 girls 3/5 boys.

So now you want the probability of getting boys and then boys again.

If it's a probability of something and something else you times them together.

So 3/5 times 3/5 = 9/25

Reply 11

shwansalah

Original post by Emilythorb

Hm I would probably say x ( x + 7 And then I'd be stuck

2x squared +7x + 6, ok first you do 2 times by the end number which makes 12

then two numbers times to make 12 and plus to make 7

4 and 3 works,

therefore we substitute it back into the equation

2x squared + 4x + 3x+ 6 ,

we factorise 2x squared + 4x and 3x + 6 seperately,

2x squared + 4x, we can take out a 2x

so

2x(x+2)

3x+6 we can take out a 3 so 3(x+2)

so answer is (2x+3) and (x+2)

Reply 12

aadil10

Original post by Emilythorb

Hm I would probably say x ( x + 7 And then I'd be stuck

A number 'squared' is written as 'x^2' btw. (edit: think I managed to do a squared symbol though)

so 2x² + 7x + 6 is a quadratic. This means you will have two brackets with x in. Because it's 2x² you will have 2x in one and x in the other like this:

(2x ) (x )

Then you need to find two numbers with multiply to make the number on the end (6) and add/total to make the number in the middle (7). The best way to do this is to use two factors of the end number (6) and try them out. e.g. 3 and 2.

Because the end number of the equation is positive (2x² + 7x + 6) the two numbers you picked will go into the bracket as positive like this:

(2x + 2) (x + 3)

If you expand this however you get 2x² + 6x + 2x + 6 which is 2x² + 8x + 6.
You have made the 3rd number but not the 2nd.

If you try switching the numbers like this:

(2x + 3) (x + 2)

It expands to 2x² + 4x + 3x + 6 which is 2x² + 7x + 6, the original equation.
So (2x + 3) (x + 2) is the factorised equation.

Hope this made sense :smile:

(edited 8 years ago)

Reply 13

Emilythorb

Original post by aadil10

I understand all of this but I don't understand how you managed to get it back to 7x??

Reply 14

aadil10

Original post by Emilythorb

I understand all of this but I don't understand how you managed to get it back to 7x??

Okay so the factorised equation is (2x + 3) (x + 2)

When you expand it you have to multiply all the left side by all the right side:

2x X x = 2x²

2x X 2 = 4x

3 X x = 3x

3 X 2 = 6

so you have 2x² + 4x + 3x + 6

The '4x + 3x' simplifies to '7x'

so you get 2x² + 7x + 6

Reply 15

joe4234

Original post by shwansalah

Exam tommorow and i'll be glad to help with your revision, so fire away.

How do I factorise equations such as 2x^2-7x+3

I know how to regular ones that have a single x^2 but when they're like this with more than one x^2 then I have no idea. Can you link me to some help or explain this for me?

Reply 16

shwansalah

2x squared - 7x+3

FIRST, you do the first number times the end number, ( 2 TIMES 3= 6)

SECONDLY, two numbers that times to make 6 and plus to make -7, the answer is -6 and -1

THRIDLY, the expression was 2x squared -7x + 3,

NOW it becomes 2x squared -6x -1x +3 , ( we split the -7x into -6x and -1x)

NOW we factorise each part seperately

so we first factorise 2x squared -6x which is 2x(x-3)

Then we factorise the -1x + 3 which is -1(x-3)

which becomes (2x-1) and (x-3) which is ur final answer

Reply 17

shwansalah

Original post by joe4234

Forgot to reply directly to you, woops, anyway the solution is above ^^^^

Reply 18

*SweaterWeather*

Original post by aadil10

uhmmm sorry, but for this question wouldnt the probability be slightly less than that?

If you don't simplify it, just so it's clearer to see:

so 4/10 girls, and 6/10 boys
P(boy) on the first choice = 6/10
but P(boy) on second choice (assuming a boy was chosen the first time) would be 5/9 as one boy has been picked so cannot be picked again?
So the overall probability would be 5/9 x 6/10, which is 1/3 :smile:

Sorry if this is over complicating stuff :frown:

Reply 19