gcse maths question

zenith10 · 12 Jun 2006 at 14:28

i had my maths gcse paper 2 today and it was the calculator one
this question come up and im just wondering if im right?

area = 10
am i right in thinking that x = 2
because area of a rectangle = height x width and area of triangle is half base x height?

Grrrrr · 12 Jun 2006 at 14:31

I think you've missed part of the question out...?

daz · 12 Jun 2006 at 14:34

Where's the rest of the question?

zenith10 · 12 Jun 2006 at 14:34

it just said work out x?

spirit · 12 Jun 2006 at 14:36

yeah whats the area, and no you are wrong, if you used are of rectangles alone.

use area of trapezoid, or area of rect - tri (will come to the same thing)

area = 1/2(a+b)h = x²+1.5x

you have to actually equate that to the area you are given.

Grrrrr · 12 Jun 2006 at 14:39

The area is

x*(x+1) + (1/2)x = x^2 + (3/2)x

and that's about all you can work out

Dave · 12 Jun 2006 at 15:06

^ should be 3/2, not 5/2

I'm guessing it's then a case of equating it to a value they give you for the area. You can't solve for x if you have nothing to equate it to.

Vonhelmet · 12 Jun 2006 at 15:18

I think there's part of the question missing... Did it give you the area, from which to work out X? What does X represent?

stig · 12 Jun 2006 at 15:22

yeh your missing an area , we cant tell you X without at least that!

zenith10 · 12 Jun 2006 at 15:35

i dont think ive left anything out ill have a think about it

sinister_stu · 12 Jun 2006 at 16:11

zenith10 said:
i dont think ive left anything out ill have a think about it

Maybe you have done...

The expression for A is a quadratic for which you can solve x, but only if it's equated to something.

zenith10 · 12 Jun 2006 at 17:50

thats what i missed out lol
that the area = 10
sorry so im sure x = 2

spirit · 12 Jun 2006 at 17:52

x²+1.5x - 10 = 0
x = 2.5 (or -4)

oops

mc_bob · 12 Jun 2006 at 17:53

Isnt it about 2.333... just looking at it.

MC_Bob

EDIT - no sorry it isnt lol. Will think about this.

Inquisitor · 12 Jun 2006 at 17:56

x² + 3x/2 = 10
x² + 3x/2 - 10 = 0

If we substitute x = 2 into this equation, we get -3 = 0, so x != 2

(can't be arsed to work out the possible values of x at the moment.)

spirit · 12 Jun 2006 at 17:57

i've solved it, whats the problem?

Dave · 12 Jun 2006 at 18:07

spirit said:
x²+1.5x - 10 = 0
x = 2.5 (or -4)

oops

Yup

Inquisitor · 12 Jun 2006 at 18:10

spirit said:
i've solved it, whats the problem?

You beat me to it

spirit · 12 Jun 2006 at 18:14

Inquisitor said:
You beat me to it

lol sorry

zenith10 · 12 Jun 2006 at 18:57

lol wish i looked at it properly now. will still get marks for showing my working anyway because i knew what i was doing but ended with the wrong answer