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# some questions that need to be done. Watch

1. Q1. rearange S=2pidsqrthh^2+d^2 i need to make h the subject.

so far i've got s^2=(2pid)^2 (h^2+d^2)

i'm not sure if i'm doing it correctly.

Q2. solve the equation

7/x+2 + 1/x-1 = 4

so far i've got

7x-7 = 4x^2+4x-8 then 4x2-3x-1=0

factorised it

-3+or-(sqrt3^2-4x4x-1)/8

i got x = 0.25 or -1 which i think is wrong.

Q3. bag contains 6 red disks, 4 blue disks and 5 green disks.
A fair dice has 4 red faces and 2 blue faces.

a disk is taken at random from bag and the colour is recorded.
then dice is thrown twice and each time colour of face it lands on is recorded.

work out probability that, of the three colours that are recorded, exactly 2 are the same.
2. (Original post by non)
Q1. rearange S=2pidsqrthh^2+d^2

so far i've got s^2=(2pid)^2 (h^2+d^2)

i'm not sure if i'm doing it correctly.

Q2. solve the equation

7/x+2 + 1/x-1 = 4

so far i've got

7x-7 = 4x^2+4x-8

factorised it

-4+or-(sqrt4^2-4x4x-8)/8

i got x = 1 or -2 which i think is wrong.

Q3. bag contains 6 red disks, 4 blue disks and 5 green disks.
A fair dice has 4 red faces and 2 blue faces.

a disk is taken at random from bag and the colour is recorded.
then dice is thrown twice and each time colour of face it lands on is recorded.

work out probability that, of the three colours that are recorded, exactly 2 are the same.
I can't understand what you have to rearrange in question 1

For question 2, you haven't got the right answer Firstly, you got the LHS wrong (7x-7). After correcting that,you need to rearrange the equation to get 0 on one side before you use the quadratic formula or factorise. Oh, and you said that you factorised 4x^2+4x-8 it but you actually used the quadratic formula.

I need to go away for a bit now but if I come back before anyone else answers, I'll look at question 3
3. (Original post by usycool1)
I can't understand what you have to rearrange in question 1

For question 2, you haven't got the right answer You need to rearrange the equation to get 0 on one side before you use the quadratic formula or factorise. Oh, and you said that you factorised 4x^2+4x-8 it but you actually used the quadratic formula.

I need to go away for a bit now but if I come back before anyone else answers, I'll look at question 3
thanks i did what you said and made it = 0 then factorised it but now i've got x=-1 or 0.25 which i don't think is correct.

for q1 i need to facvtorsie to make h the subject.
4. (Original post by non)
thanks i did what you said and made it = 0 then factorised it but now i've got x=-1 or 0.25 which i don't think is correct.

for q1 i need to facvtorsie to make h the subject.
For question 1, do you have to rearrange this:

Or something else?

EDIT: For question 2, you have got the left hand side wrong (7x-7) initially. That's where you made the mistake, maybe if you post your working I can see where you've gone wrong
5. (Original post by usycool1)
For question 1, do you have to rearrange this:

Or something else?

EDIT: For question 2, you have got the left hand side wrong (7x-7) initially. That's where you made the mistake, maybe if you post your working I can see where you've gone wrong
yes that is what i have to rearange. i don't really understand both questions 2 and 3.
6. (Original post by non)
yes that is what i have to rearange. i don't really understand both questions 2 and 3.
OK, lets do each question one at a time. For question 2, I posted an example here. Have a look at it and then see if that helps you to answer question 2. If any step confuses you, ask me and I'll explain it in more detail.
7. (Original post by usycool1)
OK, lets do each question one at a time. For question 2, I posted an example here. Have a look at it and then see if that helps you to answer question 2. If any step confuses you, ask me and I'll explain it in more detail.
so i'm not sure how to start it i thought that you should multiply 7 by x-1.
8. bump
9. (Original post by non)
so i'm not sure how to start it i thought that you should multiply 7 by x-1.
You have to multiply everything by a common denominator. The common denominator in this case would be (x+2)(x-1).

So you multiply everything by (x+2)(x-1).

Imagine if we had the question: . To get the answer 7, we would cancel the 3's, right?

The same applies here:

would cause the (x+2)'s to cancel, leaving us with .

So in essence, we are multiplying the 7 by (x-1) but it's important to realise that you're actually multiplying everything by (x+2)(x-1).

See the spoiler if you're confused.

Spoiler:
Show

Multiply everything by (x+2)(x-1):

Cancel the common terms:

Now expand the brackets
10. (Original post by usycool1)
You have to multiply everything by a common denominator. The common denominator in this case would be (x+2)(x-1).

So you multiply everything by (x+2)(x-1).

Imagine if we had the question: . To get the answer 7, we would cancel the 3's, right?

The same applies here:

would cause the (x+2)'s to cancel, leaving us with .

So in essence, we are multiplying the 7 by (x-1) but it's important to realise that you're actually multiplying everything by (x+2)(x-1).

See the spoiler if you're confused.

Spoiler:
Show

Multiply everything by (x+2)(x-1):

Cancel the common terms:

Now expand the brackets
4x^2=4x-8

thank you but what should i do next?
11. (Original post by non)
4x^2=4x-8

thank you but what should i do next?
Good, but you have to expand all the brackets. After doing that, rearrange the equation to get 0 on one side. See my example under where it says "Simplify it" and "Rearrange the equation to get 0 on one side" if you're unsure what you're supposed to do
12. (Original post by usycool1)
Good, but you have to expand all the brackets. After doing that, rearrange the equation to get 0 on one side. See my example under where it says "Simplify it" and "Rearrange the equation to get 0 on one side" if you're unsure what you're supposed to do

Updated: June 20, 2012
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