GCSE Question

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.

(edited 11 years ago)

For question two wouldn't you * the botoms by eachother

OP

Original post by Mrbawby

For question two wouldn't you * the botoms by eachother

i'm not sure sorry.

7/x+2+1/x-1=4
(x-1). (x+2)
(7x-7)+(x+2)/(x+2)(x-1)=4
7x-7=4x-4
7x=4x+3
3x=3
X=1
Btw i havent started unit 2 so it may be wrong

(edited 11 years ago)

Original post by Mrbawby

7/x+2+1/x-1=4
(x-1). (x+2)
(7x-7)+(x+2)/(x+2)(x-1)=4
7x-7=4x-4
7x=4x+3
3x=3
X=1
Btw i havent started unit 2 so it may be wrong

You have to multiply the 4 by (x-1)(x+2) too.

And you can't cancel out (x+2) in the lines in bold :smile:

:smile:

(edited 11 years ago)

Nope, i *7 by x-1 and 1 by x+2 buy like i said i may be wrong

Original post by Mrbawby

Nope, i *7 by x-1 and 1 by x+2 buy like i said i may be wrong

Ah, I see. You have to multiply the 4 by (x-1)(x+2) too :smile:

:smile:

Uh you sure 7(x-1)+1(x+2)/x^2+x-2=4 right? Mind doing the question for us

Original post by Mrbawby

Uh you sure 7(x-1)+1(x+2)/x^2+x-2=4 right? Mind doing the question for us

I'll post a different example and you guys can try the original question on your own :smile:

:smile:

Spoiler

OP

Original post by usycool1

I'll post a different example and you guys can try the original question on your own :smile:

:smile:

Spoiler

thanks i think i've got it. 0.95 and -1.70

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