Question

If someone could help me get started with this one please?

Find the slope of the line that passes through the pair of points (-a+1, b-1) and (a+1, -b)

Answer 1

I know to use y=mx+b, but where would I start with this one?

Answer 2

slope=(y_step)/(x_step)
so here slope=(-b-(b-1))/(a+1-(-a+1))=1/2a

Answer 3

Thanks, give me a few minutes and I'll post what I come up with.

Answer 4

\[m=\frac{ 2b-1 }{ 2a+1 }\]

Answer 5

I can show my work if need be...

Answer 6

the y_step is -b-(b-1)=1 the x_step is a+1-(-a+1)=2a

Answer 7

So you're saying that the answer is \[\frac{ 1 }{ 2a }\] ?

Answer 8

yes

Answer 9

that isn't one of the answer choices...

Answer 10

what choices are there?

Answer 11

give me a little bit, I type slow and there are 5 choices...lol

Answer 12

ah. I'm totally stupid :D it's (-2b+1)/2a

Answer 13

\[m=\frac{ 1-2b }{ 2a }, m=\frac{ 2b-1 }{ 2a }, m=\frac{ 2b }{ 1-2a }, m=\frac{ 2a }{ 1-2b }, m=\frac{ 1-2b }{ 2a+1 }\]

Answer 14

so, A is the correct answer?

Answer 15

yes

Answer 16

ok... i went wrong big time somewhere, because i came up with B

Answer 17

and I just saw where I went wrong...lol

Answer 18

there are 2 points, A and B. let the coordinates of A be x1 and y1, and the coordinates of B be x2 and y2. the slope is (y2-y1)/(x2-x1) or (y1-y2)/(x1-x2) but (y2-y1)/(x1-x2) is not the same, it's the opposite ;)

Answer 19

yeah, I forgot basic algebra...lol
here is what I initially came up with using y=mx+b:
\[m=\frac{ b }{ a+1 }-\frac{ b-1 }{ -a+1 }=\frac{ 2b-1 }{ 2a }\]

Answer 20

Once I use basic algebra, I came up with (still using y=mx+b) \[m=\frac{ 1-2b }{ 2a }\]

Answer 21

good for you :)

Answer 22

Thanks for your help!

Answer 23

you are welcome