Question

Need help with an equation!

Solve the equation x(m+7)+y(m-2)=z(m-9) for m, assuming that x+y-z is not equal to 0.

Please show me step by step not just the answer

Answer 1

you need to collect the terms involving "m".

so first step would be to expand the brackets.

Answer 2

can you do that?

Answer 3

like multiply it out?

Answer 4

yes

Answer 5

Yep gimme a second

Answer 6

ok :)

Answer 7

xm+7x+ym-2y=zm-9z

Answer 8

good, now try to get all terms involving "m" to the left-hand-side and all the rest of the terms on the right-hand-side of the equals sign

Answer 9

xm+ym-zm=-9z-7x+2y

Not sure if I did that right

Answer 10

looks good to me. :)

next - factor the m out on the left-hand-side

Answer 11

m(x+y-z)=-9z-7x+2y

Answer 12

perfect - now divide both sides by (x+y-z)

Answer 13

m=(-9z-7x+2y)/(x+y-z)

Answer 14

thats it!

can you see why the question stated: "assuming that x+y-z is not equal to 0" ?

Answer 15

Hmm, I'm still not sure why it said that

Answer 16

think about this:

x = something / 0 = ?

Answer 17

I meant to say:

m = something / 0 = ?

Answer 18

if you have an equation like this:

17 * 0 = 16 - 15 - 1

then it does NOT imply that:

17 = (16 - 15 - 1)/0

Answer 19

because ANYTHING divided by zero is infinity

Answer 20

in algebra you cannot divide by zero - that is not a legal operation to perform

Answer 21

Ah I think I see what you're saying now

Answer 22

great!

just one more point - the "standard" way of writing the answer is as follows:

m=(-7x+2y-9z)/(x+y-z)

i.e try to list the unknowns in alphabetical order

Answer 23

what you wrote is still correct - what I suggested is just the "normal" practice in algebra

Answer 24

its not a hard and fast rule though

Answer 25

Oh I didn't know that. =p
Thanks so much for the help, I was stuck on that problem for a while. I get lost in all the letters

Answer 26

yw :)