# Boards

## Could you work this out:

x^2 - 10x + 18 = (x-a)^2 + b

To find a and b.

Uproar on a local forum that the SQA Scottish Standard Grade exam contained this and that it was a Higher grade question. Well if this is uni entry standard i.e. Higher than I don't know what this country is coming to...

## I hope so

## Do it!

## I don't really understand the problem

It's completing the square. The same thing's on the A-level maths syllabus. It's a bit walked-through perhaps, but that's it.

## OH YEAH

now i remember.

easy fucking question. IF I COULD BE BOTHERED.

## well, it's pretty unfair to expect people who haven't been taught how to do it, to y'know, answer th

and anyway, that's one of the simplest questions (eie. worth 2/3 marks) that was on the higher paper when i sat it last year.

for the record, i can make it to about the third or fourth line of working and then i can't remember what i'm meant to do after it. OH NOEZ HOW WILL I POSSIBLY GET AHEAD IN LIFE????????

## the bloody thing*

## DA ANSWER IZ

23827878

## the answer is 17

it's ALWAYS 17!

## I reckon if you put 42 as every answer on a maths/physics paper

geek solidarity means they'd at least have to give you a D.

## :D

I did a class called Exploring the Cosmos in first year uni. The class test was worth 20% and was completely multiple choice.

Statistically, if you put A, B, C or D for every answer you were very likely to get 25%.

I preferred to draw pretty pictures with my multiple choice guesses.

## Those sort of tests

usually use negative marking so you'd usually average 0 though. Ours always did.

## nope, i can't

## a 16 year old should be able to do that

...

## my thoughts exactly lyle

## ^ Yep,

but I wouldn't expect an over 16 year old who hasn't touched a maths book in years to be able to do it.

If you can then big fucking whoop.

## what does this ^ mean?

## The "^" in the maths question?

to the power of.

## I could porbably have done this

2 years ago, but I've spent so long not doing maths I forgotten it all :(

## To the power of, presumably

## oh.

how I got an A in GCSE maths is completely beyond me. I have no idea where to even begin with that problem.

## Damn

I thought I could remember how to do this, but so far all I've got is:

18-10x = a(a-2x)+b

Which doesn't help anything, I think...

Just over two years ago I was doing higher maths at A level, but already forgotten it all. Damn.

## im now 25

i wouldnt even know where to start anymore.

## a=5

b=-7

## ^alan turing

## I'm sitting advanced maths a week on tuesday

then no maths EVER AGAIN!

YAY!

## Anybody who's done A-level maths

should be able to do that no problem. Even if you don't now the 'proper' method for solving it just multiply out the right hand side and it becames obvious what a and b are.

## I didn't do anything further than standard grade maths.

So, I probably couldn't do this, no. :(

## nope not a chance

I only made it as far as scraping a C at GCSE - I'd stand a better chance of reading French and I haven't done that since I was 13 or 14.

## this is awful

I got A* at GCSE, A at A-Level (needing -3 when I sat my last paper), and I don't have a fucking clue how to do this :( Someone explain?

## Well as it's (x-a)^2

that is basically (x-a)(x-a)

I.e when multiplied out becomes

X^2-2ax+a^2

as -2ax corresponds with the -10x on the other side, equate the coefficients

-2a=-10

a=5

then you put that into the main equation and you get 25, so you have to minus to get 18, therefore b=-7

pretty easy.

## yeah but

how can you just take the '18' and 'b' term out of the 'main equation' like that?

Surely if you multiply out the brackets you get

x^2 - 10x + 18 = x^2 - 2ax + a^2 + b

from there, how do you argue that "-2ax corresponds with -10x on the other side"?

## because "-2ax" is the only term on the other side containing an x term

## yep

you're right. Absolute concrete proof that I don't remember anything from A-Levels.

## Like I said

I don't know if this is the 'proper' way that people are taught but multiplying out the right hand side you get x^2 - 2ax + 25 + b.

You see on the left hand side you have a 10x therefore 2a = 10 so a = 5

Also from the lhs you see you have 18 added to the x^2 - 10x, therefor 25 + b = 18 so b = 18 - 25 = -7

## it's pretty common to include

questions that would usually be 'above' the level of teaching, to highlight those who have indulged in extra study

it seperates the A's from the A*'s

## No

I wouldn't even know where to start.

## That's not even remotely hard

I don't get it.

Why is there outrage? It's just really basic foundation stuff, you'd expect it to be in a test as a starter but it certainely isn't difficult.

## Is higher GCSE or A-level?

## Higher is in between GCSE and A level

## Oh right

sounds about right then.

## that's not true

## Accountantcy is not the height of mathmatical application

## accountancy

## My dad's a high-flying city type Finance Director

He left school with only a handful of O levels, failing maths. 40 years later and he's on a six-figure salary, but he still doesn't understand algebra.

## Yeah

That's not surprising. If he was an engineer or something it would be.

## I have no idea now

as I haven't used Algebra for years.

A few years back when I was using it at A-Levels/Uni I would probably have had no probs.

I suppose that's the problem of learning things you never use.

## Not a chance

but as I haven't touched any maths problems since I got a lowly 'C' at O level 24 years ago (yes I'm that old!) I'm not that bothered!