# Thread: Co ordinate geometry

1. ## Co ordinate geometry

Ok so i have encountered a problem! The question is the points a(6,1) B(2,-1) (a) find eq of line for AB. I done this got the slope as -2/-4 or 1/2. and worked out the eq of line to be x -2y -4 =0 but the part b is where im finding difficulty it asks (b) The line AB crosses the y-axis at C. Find the co-ordinates of C. I don't know i was thinking that means the x=0 but don't know how to get the other value

2. ## Re: Co ordinate geometry

Hey dcmath.

You are right in that plugging in x = 0 gives the y co-ordinate (call it y0) and the point C will be C = (0,y0)

3. ## Re: Co ordinate geometry

The other method could be that we write the equation of line in intercept form i.e., x/a + y/b = 1 where a and b are the intercepts on x axis and y axis respectively. On writing the equation in this form we get x/4 + y/(-2) = 1 so we get the y intercept as -2 and coordinates of point C will be ( 0,-2 )