# work out the co ordinates

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• Apr 7th 2011, 10:15 AM
andyboy179
work out the co ordinates
hi,

i need to work out the co ordinates of two points that the graph of y=2x-1 passes through.

i don't really know how to do this so could somone explain what i have to do please?!?

thanks!
• Apr 7th 2011, 10:55 AM
e^(i*pi)
Pick any old values of x and put the corresponding y value in.

For example (0,-1) is a point on the line
• Apr 7th 2011, 10:59 AM
andyboy179
oh so would (1, -1) be one aswell?
• Apr 7th 2011, 11:10 AM
TheChaz
Quote:

Originally Posted by andyboy179
oh so would (1, -1) be one aswell?

No. (x, y) = (1, -1) is NOT on the line since using these values in
y = 2x - 1 gives us
-1 = 2(1) -1, which is FALSE.
• Apr 7th 2011, 11:11 AM
e^(i*pi)
No, what makes you say that?

The equation is a straight line. If you want to use x=1 then it would be $\displaystyle (1, [2 \cdot 1 - 1])$
• Apr 7th 2011, 11:15 AM
andyboy179
would (-1,0) work?
• Apr 7th 2011, 11:17 AM
e^(i*pi)
Quote:

Originally Posted by andyboy179
would (-1,0) work?

Sub it into the equation and check. Does $\displaystyle (2 \times -1) -1$ equal 0?
• Apr 7th 2011, 11:18 AM
TheChaz
When x = -1,
y = 2x - 1 becomes
y = 2(-1) - 1 =
-2 -1 = -3
S0 (-1, -3) is the point
• Apr 7th 2011, 11:19 AM
andyboy179
oh i see now, thanks alot!
• Apr 7th 2011, 11:32 AM
andyboy179
no its -1
• Apr 7th 2011, 11:42 AM
veileen
Uhm, you don't simply search numbers that verify the equation, but take the intersection with the axes (make x=0 and find y, then make y=0 and find x).
• Apr 7th 2011, 11:47 AM
NOX Andrew
That's only necessary to find the x- and y-intercepts. For any two points on the line, any two values of x suffice.
• Apr 7th 2011, 10:44 PM
CaptainBlack
Quote:

Originally Posted by andyboy179
oh so would (1, -1) be one aswell?

Quote what you are responding to otherwise the thread will become confusing.

CB
• Apr 7th 2011, 10:45 PM
CaptainBlack
Quote:

Originally Posted by e^(i*pi)
No, what makes you say that?

The equation is a straight line. If you want to use x=1 then it would be $\displaystyle (1, [2 \cdot 1 - 1])$

Quote what you are responding to, otherwise the thread will become incomprehensible.

CB
• Apr 7th 2011, 10:45 PM
CaptainBlack
Quote:

Originally Posted by andyboy179
would (-1,0) work?

Quote, or don't bother replying thank you.

CB
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