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# GCSE Maths Questions watch

1. Hi, ive been doing practice questions for maths and have been fine with all of them except these three and would be grateful if someone could show me how to do them
1) 4n^2/3=8^-1/3 Find the value of n

2) The diagram shows a sketch of the graph y=ab^x
The curve passes through the points A(0.5,1) and B(2,8)
The point C(-0.5,k) lies on the curve
Find the value of k

3)Solve 2x^2+8x-3=0
Give your answers in the form p+or- square root of q/r where p,q and r
are integers
This one has to be done by completing the square
Thankyou
2. Can you put some brackets in 1) as your notation is ambiguous?

2) Substitute your points into the equation and form a pair of simultaneous equations. Now how might you solve them to find the values of a and b?

3) It doesn't have to be done by completing the square (unless the question says so). You might find the quadratic formula easier.
3. (Original post by Ginger_Gymnast92)
Hi, ive been doing practice questions for maths and have been fine with all of them except these three and would be grateful if someone could show me how to do them
1) 4n^2/3=8^-1/3 Find the value of n

2) The diagram shows a sketch of the graph y=ab^x
The curve passes through the points A(0.5,1) and B(2,8)
The point C(-0.5,k) lies on the curve
Find the value of k

3)Solve 2x^2+8x-3=0
Give your answers in the form p+or- square root of q/r where p,q and r
are integers
This one has to be done by completing the square
Thankyou
Do you mean
4. (Original post by Mr M)
Can you put some brackets in 1) as your notation is ambiguous?

2) Substitute your points into the equation and form a pair of simultaneous equations. Now how might you solve them to find the values of a and b?

3) It doesn't have to be done by completing the square (unless the question says so). You might find the quadratic formula easier.
1) sorry, do you mean like this? 4n^(2/3) = 8^ -(1/3)

2) like this ? , 1=ab^0.5
8=ab^2

1=ab^ (1/2) = square root of ab
8=ab^2

7=ab^2 - square root of ab ?

I don't think i've done that right

3) it was in the completing the square part of the book so i presumed it had to be. I did this

x^2+4x-1.5=0
(x+2)^2 -2.5 =0
(x+2)^2 = 2.5
(x+2) = square root of 2.5
x = 2 +or- square root of 2.5

and then got stuck?
5. (Original post by reubenkinara)
Do you mean
yes, sorry i don't know how to write it like that on a keyboard
6. (Original post by Ginger_Gymnast92)
1) sorry, do you mean like this? 4n^(2/3) = 8^ -(1/3)

2) like this ? , 1=ab^0.5
8=ab^2

1=ab^ (1/2) = square root of ab
8=ab^2

7=ab^2 - square root of ab ?

I don't think i've done that right

3) it was in the completing the square part of the book so i presumed it had to be. I did this

x^2+4x-1.5=0
(x+2)^2 -2.5 =0
(x+2)^2 = 2.5
(x+2) = square root of 2.5
x = 2 +or- square root of 2.5

and then got stuck?
Can we deal with them one at a time as this is getting confusing?

7. (Original post by Ginger_Gymnast92)
2) like this ?
1=ab^0.5
8=ab^2
This is right. Now you don't want to SUBTRACT the equations, you want to DIVIDE the second by the first.
8. The first question is very difficult.

a) Evaluate the right hand side

b) Divide both sides by 4

c) Cube both sides

d) Square root both sides

e) Rationalise the denominator
9. (Original post by Mr M)
Can we deal with them one at a time as this is getting confusing?

oh so it would be (x+2)^2-5.5=0
x= -2 +or- square root of 5.5
x= -2 +or- square root of (11/2)
10. (Original post by Ginger_Gymnast92)
oh so it would be (x+2)^2-5.5=0
x= -2 +or- square root of 5.5
x= -2 +or- square root of (11/2)
I've just noticed you are now solving a different question to the one you provided in your opening post. Which one is correct?
11. (Original post by Mr M)
This is right. Now you don't want to SUBTRACT the equations, you want to DIVIDE the second by the first.
8=ab^2 divide by
1=ab^0.5

8=ab^(3/2) ?

12. (Original post by Ginger_Gymnast92)
8=ab^2 divide by
1=ab^0.5

8=ab^(3/2) ?

Nearly. What is when ?
13. (Original post by Mr M)
I've just noticed you are now solving a different question to the one you provided in your opening post. Which one is correct?
I halved the original question so i could use completing the square
14. (Original post by Ginger_Gymnast92)
I halved the original question so i could use completing the square
Fair enough - I was being dim not to realise what you were doing.

You have ambiguous notation in your question again.

Is the square root supposed to apply to (q/r) or just to q?

I ask because I don't know whether you need to rationalise the denominator of your surd or not.
15. (Original post by Mr M)
Fair enough - I was being dim not to realise what you were doing.

You have ambiguous notation in your question again.

Is the square root supposed to apply to (q/r) or just to q?

I ask because I don't know whether you need to rationalise the denominator of your surd or not.
the square root is meant to apply to (q/r)
16. (Original post by Mr M)
Nearly. What is when ?
1?

8=ab^2
1=ab^0.5

can i cancel the a to make

8=b^(3/2) ?
17. (Original post by Ginger_Gymnast92)
1?

8=ab^2
1=ab^0.5

can i cancel the a to make

8=b^(3/2) ?
Yes now square both sides and then cube root both sides to find b.

You can then substitute back into one of the original equations to find a.
18. (Original post by Ginger_Gymnast92)
the square root is meant to apply to (q/r)
Then you have finished 3).
19. (Original post by Mr M)
Yes now square both sides and then cube root both sides to find b.

You can then substitute back into one of the original equations to find a.
okay think i get how to do it now thankyou

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