Posted by emma green on .
decide whether the graphs of the two equations are parallel lines:
1. 2x+3y=5
9y+6x1=0
answer: yes
2. 15+3x10y=0
30x+24=10y
answer: yes
please check if this is right. thanks

maths 
MathMate,
1. correct.
2.
When the lines are given in standard form (Ax+By+C), they are ideal for checking parallelism and perpendicularity because if there is a vertical line, the y term will simply disappear, i.e. B=0, while in the slopeintercept form, the slope m will become infinity, which is not the case here.
For checking parallelism, try to multiply or divide to equalise one of the two coefficients, A, or B, and compare the other one. C will be different for parallel lines.
15+3x10y=0....(1)
30x+24=10y ....(2)
becomes
3x10y+15 = 0, and
30x10y+24 = 0
We see that B is equal while A is different, we conclude that the two lines are not parallel. 
maths 
emma green,
thank you! :)

maths 
MathMate,
You're welcome!