I know the formulas for coordinate geometry of the straight line and I've done a fair bit of it but I have trouble when it comes to converting equations into lines with coordinates.(adsbygoogle = window.adsbygoogle || []).push({});

Heres an example of a question I can't answer

L is the line 2x - 3y - 7 = 0. Verify that the point a(-1,-3) is in L.

Find

i) the slope of L

ii) the coordinates of the points where L intercepts the y-axis

iii) the equation of the line parallel to L through the point (-3,0)

First off I assume that to verify (-1,-3) is on the line L I just plug those values into the equation for L. I did that and the answer comes out to 7 not 0 so I assume (-1,-3) is not on the line.

i) To find the slope I would use the formula-a/bwhich would give me -2/3. Another way I'd get the slope is to rearrange the equation into y = m(x) form and doing that I get the same result -2/3. Is this correct?

ii) To find the y intercept of a point I would arrange the equation into its slope intercept form and heres what I gety = -2/3(x) + 7so in this case I'd assume the y intercept is 7 but this seems to be incorrect

iii) for this one I'd use the formulay - y1 = m(x - x1)

So the main part of this I'm having trouble with is finding the y intercept of line L because if I try to get it by letting y in the equation = 0 I get a different answer to 7.

I also don't get why they say "verify" that points on the line if it isn't even on the line. I woulda thought they'd say "find out if point (-1,-3) is on L"

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Couple of questions on linear geometry

**Physics Forums | Science Articles, Homework Help, Discussion**