Am I just being stupid? GCSE Maths help!

Meatball · 5 Jun 2006 at 11:15

I'm completely stuck on this question: (Parts I don't understand in pink)

On the table I can't understand how they got the Y value's they got?

Formula to get y: Y= 25x -5xsquared
So if x is 2:
25x(50)-5xsquared(100) = -50

yet the book got 30? Is is a case of not working out the Y values through the formula but from the graph?

Raikiri · 5 Jun 2006 at 11:19

x^2 when x =2 is 4

4x5 = 20

50 - 20 = 30

benjo plz. · 5 Jun 2006 at 11:19

When x is 3.6 y is 26.
When x is 1.4 y is 25.2.

Add and divide to average?

loopylou · 5 Jun 2006 at 11:20

Use the table.

benjo plz. · 5 Jun 2006 at 11:21

loopylou said:
Use the table.

Nah, that's for the curve

.

Raikiri · 5 Jun 2006 at 11:21

So to summarize, yes you are just being stupid

Meatball · 5 Jun 2006 at 11:21

Raikiri said:
x^2 when x =2 is 4

4x5 = 20

50 - 20 = 30

I'm sorry but I don't understand that, my maths is bad sorry

. x^2 means X squared right? 5 2s squared = 10x10=100? Grrr damb my small brain

Raikiri said:
So to summarise, yes you are just being stupid

thought so

Raikiri · 5 Jun 2006 at 11:22

Yep, you do the power first then times that by the value (amount)

Also I'm so happy I didnt take A level maths

Unconditional · 5 Jun 2006 at 11:23

Lost-Prophet said:
Formula to get y: Y= 25x -5xsquared
So if x is 2:
25x(50)-5xsquared(100) = -50

How on earth did you get 5x^2 equal to 100 when x = 2?

2*2*5 = 20.

50-20 = 30.

Meatball · 5 Jun 2006 at 11:24

Unconditional said:
How on earth did you get 5x^2 equal to 100 when x = 2?

2*2*5 = 20.

50-20 = 30.

I always thought when you had something like 4x^ you would work out what four x's squared is (so if x was 3 you do 3x3=9) and then square 9 (9x9=81)

Got it now:

when x = 4

Y= 25x - 5x^

25x4 = 100

4x4=16 x 5 = 80

Y = 25x(100) - 5x^(80)=20?

Hate · 5 Jun 2006 at 11:30

how did you think it was the Y value when it clearly says x? :s

ballistic · 5 Jun 2006 at 11:34

-50? wtf

Raikiri · 5 Jun 2006 at 11:35

He done (5 x X)^2

Minto · 5 Jun 2006 at 11:36

Lost-Prophet said:
I always thought when you had something like 4x^ you would work out what four x's squared is (so if x was 3 you do 3x3=9) and then square 9 (9x9=81)

Got it now:

when x = 4

Y= 25x - 5x^

25x4 = 100

4x4=16
16 x 5 = 80

Y = 25x(100) - 5x^(80)=20?

why on earth are you multiplying by 25 and 5 again, you already did that above. (unless of course the things in brackets are meant to show what 25x and 5x^2 are, but if so don't write it like that in your exam.)
100-80=20

crunchman · 5 Jun 2006 at 11:37

Lost-Prophet said:
I always thought when you had something like 4x^ you would work out what four x's squared is (so if x was 3 you do 3x3=9) and then square 9 (9x9=81)

Got it now:

when x = 4

Y= 25x - 5x^

25x4 = 100

4x4=16 x 5 = 80

Y = 25x(100) - 5x^(80)=20?

Yup that's correct.

crunchman · 5 Jun 2006 at 11:39

Minto said:
why on earth are you multiplying by 25 and 5 again, you already did that above. (unless of course the things in brackets are meant to show what 25x and 5x^2 are, but if so don't write it like that in your exam.)
100-80=20

He's only showing the answer in brackets, but I agree it would be confusing to the examiner.

Treefrog · 5 Jun 2006 at 12:05

Hehe - the ^2 only applies to the x, not to 5x

General rule: if it was the 5x that was squared there would be brackets round the 5x; as there aren't it's just the x that's squared.

crunchman · 5 Jun 2006 at 16:55

How was the exam ?

Meatball · 5 Jun 2006 at 16:58

crunchman said:
How was the exam ?

thanks for asking. Errr.. it wasn't easy

. Most people came out with the same feelings as me, challenging springs to mind :eek:

Smithy · 5 Jun 2006 at 17:08

lol, oh how i wish i could take my GCSE maths exam again. Doing A-Level maths for 2 years its surprising how incredibly easy questions like the one in the OP become.
Its always better when everyone else comes out of the exam with the same feeling as you though, makes you feel somehow less stupid.