flummoxed by sons revision question

[Sp!ke]

I was scratching my head on this one for a bit...

1-2(x+3)=4(x-2)+8

How many of you can solve this in 5 minutes?

 

[alistairgd]

Off the top of my head

1-2(x+3)=4(x-2)+8

1- 2x + 6 = 4x - 8 + 8

1 + 6 + 8 - 8 = 4x + 2x

6x = 7

x = 7/6

Doesn't seem right lol.

 

[alistairgd]

There's a pretty clever website that has a form that solves these things for you, found it when helping my kid a few months back, I'll see if I can find it again...

Edit, here it is

http://www.algebrahelp.com/calculators/equation/ x = -0.8333333333

or http://www.myalgebra.com/algebra_solver.aspx says the answer is the same -5/6

So I failed to simplify 1-2(x+3) and was screwed after that.

 

[Deleted member 6183]

Is this a quadratic equation?

If so, could do them at school but that was 35 years ago!

 

[Sp!ke]

I got the same answer but it was a weird one so like you I thought I got it wrong and sat all befuddled for a fair few minutes. .. good link btw, I shall not disclose it to my son

 

[ricardo62]

is there any job in real life that you need algebra for? or trigonometry for that matter

 

[alistairgd]

I got the same answer but it was a weird one so like you I thought I got it wrong and sat all befuddled for a fair few minutes. .. good link btw, I shall not disclose it to my son

What's very clever about that site (and others) is that is actually breaks it down into the steps so you can follow along, clever stuff.

 

[jotter22]

is there any job in real life that you need algebra for? or trigonometry for that matter

Yes of course there is.........



it would be a maths teacher!

 

[Sp!ke]

Surely dieselman can do it without cheating?

 

[grober]

Off the top of my head

1-2(x+3)=4(x-2)+8

1- 2x + 6 = 4x - 8 + 8

1 + 6 + 8 - 8 = 4x + 2x

6x = 7

x = 7/6



Doesn't seem right lol.

your mistake in red should be -6 -2x3=-6

 

[davidjpowell]

is there any job in real life that you need algebra for? or trigonometry for that matter

I use trig on occasions.

 

[ricardo62]

I use trig on occasions.

what job do you use trig in ?

 

[baxlin]

Don't laugh, but is the "1" at the beginning the question number (revision question, could have been copied and pasted by the teacher?), because

2(x+3)=4(x-2)+8

works out easily

 

[wemorgan]

is there any job in real life that you need algebra for? or trigonometry for that matter

Professional Engineering - admittedly there is software that does the really hard sums, but you still need to know the basics.

 

[Harley Man]

I use trig in my workshop for setting sine tables on the milling machine, also used to use it in building to calc roof angles so pretty useful stuff for me.

 

[PXW]

Don't laugh, but is the "1" at the beginning the question number (revision question, could have been copied and pasted by the teacher?), because

2(x+3)=4(x-2)+8

works out easily

Think you might be on to something here...

 

[Sp!ke]

Don't laugh, but is the "1" at the beginning the question number (revision question, could have been copied and pasted by the teacher?), because

2(x+3)=4(x-2)+8

works out easily

That sounds entirely plausible and if teached did do this then everyone will no doubt be marked wrong even if they get it right.

I shall make some enquirees.

 

[davidjpowell]

what job do you use trig in ?

Surveying. Not too often fortunately. Also get to use pi.

 

[Deleted member 65149]

The only thing I struggle with is why everyone is struggling with this! Grober spotted the mistake in Alistairgb's quick calculation, but forget to take it to the correct conclusion of x = -5/6. Simples! Surely this is basic maths. I learnt this sort of thing when I was about 11 (55 years ago) but it's so easy I don't know why others have trouble.

In answer to the question about the need for algebra and trigonometry "in real life", I use both fairly often, especially algebra. They can both be useful in calculations for building projects, or indeed any other design work. OK, so I was a telecommunications research and development engineer for most of my career so more likely to use maths than many other occupations. But it's 16 years since I left that job and I still use maths at home.

Maths has beauty and symmetry; be that the structure of right angles and circles or the balance of equations. Maths is the science of patterns - big chaotic events in the natural world can be modelled by breaking them down into the intersection of lots and lots and LOTS of little regularities. Those tiny regularities are the basis of life. There’s always symmetry in beauty. Unfortunately maths scares so many people. When they're scared they refuse to accept, learn and enjoy.

 

[grober]

Why algebra- cos its a bit like CSI --- it allows you to "profile/interrogate " = manipulate " suspects" =quantities without knowing their "identity" = value at first --by examining their "crime scene " environment/evidence and "contacts" = the equations. By combining them all together you eventually solve the case and identify the guilty party " X"