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"Help me..."

...because I'm too dim to do my maths. I'm sure it's simple really but I have:

2x(squared) + 7x - 2 = 0

When you replace x with either -2 or 1/4, the equation is correct but I can't seem to prove this using the quadratic formula or by trying to solve the equation by using brackets. Are there any other ways of proving this?
Any help would be much appreciated.

munn wrote:

> a = 2
> b = 7
> c = -2
>
> x = [-7 ± root (49-4*4*-2)]/4

That's why you got 81 instead of 65.

Well, I get it as 49 - (-16) . I'm guessing that 39 was a typo...

But anyway, back on topic, since the answer says it's 1/4 and -2, it looks like you've got it all right except you need a bracket around your first term. Don't have any pen/paper within reach and I can't do those things in my head so I'll have to assume you're simuls came out right. You need the squared to hit both the 2 and the x, which you can do by sticking a bracket around it and the squaring the bracket... follow that?

Bob_The_Moose wrote:
> Munn's method is mostly right except somehow he got an 81 instead of
> a 65 but nevermind.

Bullshat.
39-(-32) = 81

All of this has been based on my working out so far so I could be wrong I guess. The original question was using simultaneous equations:

a) y = 2x
b) y(squared) + 7x = 2

I had got it down to '2x(sqared) + 7x -2 = 0' by substituting a) into b) and therefore getting rid of 'y'. Maybe if I made 'x' the subject...

JFH wrote:
> By saying that -2 does not work, you are saying that the authors of
> "Mathematics for AQA GCSE: Higher Tier" are incorrect.

Either that or you gave us the wrong question.
It's difficult to tell you how to prove something that isn't true.

Munn's method is mostly right except somehow he got an 81 instead of a 65 but nevermind.

Of course, that's assuming you didn't mean there to be a bracket around the first term after all. Or it might be a typo in the book. And there's nothing going to make your teacher more suspicious if you somehow get the right answer when the question's been printed wrong...

Oh and just for the record, 1/4 would work if the first term was (2x)^2 not 2x^2.

I'm doing quadratics at the moment in set 1 (whoo, im wel cleva m8) and I don't get the stuff we were taught today. Not even a little bit.

Still, I pished the modules and coursework, so I should manage an A or something.

I just use the quadratic formula; it may take longer but it's much easier.

JFH wrote:
> ...because I'm too dim to do my maths. I'm sure it's simple really but
> I have:
>
> 2x(squared) + 7x - 2 = 0
>
> When you replace x with either -2 or 1/4, the equation is correct but
> I can't seem to prove this using the quadratic formula or by trying
> to solve the equation by using brackets. Are there any other ways of
> proving this?
> Any help would be much appreciated.

X = [-b ± root(b² - 4ac)]/2a

a = 2
b = 7
c = -2

x = [-7 ± root (49-4*4*-2)]/4
x = (7 + root 81)/4 or x = (7 - root 81)/4
x = (7 + 9)/4 or (7 - 9)/4
x = 16/4 or -2/4
x = 4 or -½

gamesfreak wrote:

> And guess what I got in AS Computing...
>
> ...A.

Hmm my bad.

well done on your AS grade too. I got a B.

By saying that -2 does not work, you are saying that the authors of "Mathematics for AQA GCSE: Higher Tier" are incorrect. I need a way of proving the answers, I already know what they are.

Yeah, mistake on my part, I edited it though, when I realised.

I'm busy at the moment, so I'm rushing. I'll work it out using the quadratic formula.