o level maths question

[kopend]

11) Solve the simultaneous equations:
3x - 4y = 25
4x - 5y = 32

x =
y =

[ladyalex]

x=3
y=4

Do you want the steps ?

[ladyalex]

OOps, gone wrong somewhere, I'll try again!

[ladyalex]

Are you sure that the second equation is not

4x+ 5y =32 ?

[mightyWBA]

x=3 y=-4

[ladyalex]

Or alternatively,
x=3
y= -4

[Graham-W]

x= -79
y= -68

[Graham-W]

or , probably the easier answer.

[ladyalex]

3x - 4y =25
Multiply everything by 4
gives
12x -16y =100

4x - 5y =32
Multiply everything by 3
gives
12x - 15y =96

12x-16y=100
12x-15y=96
Subtract one equation from the othr
give

0x - y =4
therefore, y =-4
If y= -4, then, looking at the first equation and substituting - 4 for y
gives
3x - 4times-4=25
3x - -16 =25
- - 16 = + 16
so
3x + 16 =25
3x = 25 -16
3x = 9
x=3

x=3, y= -4

[kopend]

I THINK I PREFER THE 3 / -4

THAN THE OTHER ONE

IT ALSO EXPLAINS WHY I WAS STRUGGLING WORKING IT OUT

I WAS TRYING EVERY COMBINATION OF POSITIVE MUMBER

NEVER THOUGHT ABOUT MINUS NUMBERS )OR NEGATIVE NUMBERS AS THEY SEAM TO CALL EM THESE DAY!

[ladyalex]

Happy to help, Kopend. Sorry about the mistake at the start.

[mightyWBA]

What do I win? :-)

[ladyalex]

Undying gratitude

[kopend]

you make it sound so simple!!

i more does "minus 4" minus "minus 4" = zero??

and "minus 4" minus "plus 4" = zero

if so if you start with "minus 4" what sum do you need to get to "minus 8" ??

[squarebear]

Yes. anything minus itself is zero.

-4 + -4 = -8

[mike11111]

I was taught: - - = +. - +/+ - = -.

[jake-the-peg]

i more does "minus 4" minus "minus 4" = zero??

- Yes minus a minus is a plus -4 - -4 =0

and "minus 4" minus "plus 4" = zero

- yes again -4 +4 is the same as swapping them around to be 4 + -4 = 0

if so if you start with "minus 4" what sum do you need to get to "minus 8" ??
if you start owing someone 4 quid you need to borrow another 4 quid to owe them 8 quid so

-4 + -4 = -8

Does that help?

[ladyalex]

Minus 4 plus minus 4 = minus 8
Minus 4 minus minus 4 =0
Minus 4 minus (plus) 4 = minus 8

Does that help at all ?

[ladyalex]

Or have I got the last one wrong ?
Head now spinning, all arithmetical skill gone.

[mike11111]

You are right as usual, milady. Rare praise from a revolting peasant.

[ladyalex]

Why thank you, Mike 111111111111

Smiles in a gracious and (hopefully) infuriating manner.