Any mathematicians?

[Peter Bell]

My Granddaughter has this maths problem, can anyone help? It seems to me there’s something missing but it’s probably me!

[emptyat]

is it at x=4 and y=3 which is where the two lines will cross?

 

(think that the other graph goes from x=10, y=9 diagonally down to x=1, y=0)

 

Edited November 22, 2020 by emptyat

[Foz]

I get it exactly the same as Emptyat (but not quite as quickly)!

[emptyat]

Sorry, should have signed properly...

Malcolm

[Peter Bell]

Many thanks chaps, I’ll pass it on but I’m still trying work out the logic! I can see the minus 1 x  0y start but the x10 9y?

[nelmo]

OK, apologies if this is very nerdy...

 

For any equation:

y=ax + b

the line crosses the y axis at b with a gradient of a. 

So, for y=x-1, the line crosses the y axis at -1 with a gradient of 1 (as it is a positive gradient, the line goes up from left to right (uphill)). 

To solve simultaneous equations, rearrange one of the equations to be 'x=' and then substitute it into the other equation, so:

Rearrange y=x-1 into:

x=y+1

Substitute back into y=7-x to give:

y=7-(y+1)

y=7-y-1

2y=6

y=3

Then put y back into the first equation, y=7-x to give:

3=7-x

x=7-3

x=4

Dull, huh? 

[richyb66]

Or

y=7-x and y=x-1 so

7-x = x-1

subtract X from both sides

7-2x = -1

subtract 7 from both sides

-2x = -8

divide both sides by -2

x=4

Substitute 4 for X in either equation

y=7-4

y=3

[Andi]

HELP 

[Peter Bell]

Makes you realise there are clever people on here many thanks!

[richyb66]

I have maths skills that I've never needed to use in the last 40 years.

[MarkBzero]

@Peter Bell I feel your pain, many years ago I was seen as a cleverest dad ever and helped with homework.

Fast forward...

Now I have a kid in college doing IT software and hardware and another in Uni doing digital forensics.

Help!!!

 

[sylvia.fry2]

3 hours ago, richyb66 said:

I have maths skills that I've never needed to use in the last 40 years.

How very true --- was using Calculus in 5th form --- could never understand the principle of there being two possible answers --- never needed to remember/use since.

And there is always an electric calculator somewhere --- if you know which buttons to press.

All present retirement calcs just need me to know the trig laws. 

[nelmo]

3 hours ago, richyb66 said:

I have maths skills that I've never needed to use in the last 40 years.

I do a weekly quiz with some old colleagues - one of the questions is a long, wordy thing that almost always requires the use of simultaneous equations to solve, so I get regular practice  .

Also a son who did his GCSEs last year and a daughter coming up to doing them now...further practice.

[richyb66]

2 hours ago, nelmo said:

I do a weekly quiz with some old colleagues - one of the questions is a long, wordy thing that almost always requires the use of simultaneous equations to solve.

Those long winter evenings must seem to fly by.

[Peter Bell]

Years ago a daughter was complaining ‘when will I ever need to use trig in real life’ so I got her to work out the camber on the front wheels on the hood!  Not sure if she ever forgave me.