Question 82103
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determine which two equations represent parallel lines
y=5/8x+3
y=-8/5x-8
y=3x+11
y=3x-3

Each of those equations is in the slope-intercept form: 

                y = mx + b

where m represents the slope and (0,b) is the y-intercept.

Lines are parallel when and only when they have the same slope.
The slope is m, the coefficient of x.

Only the last two, y = 3x + 11 and y = 3x - 3 have the same
coefficient of x, or value of m, namely 3, and this is their 
slope.  So they are the only ones which are parallel. 

<i>Incidentally, the first two are perpendicular because they have
slopes which are negative reciprocals of each other, that is,
5/8 and -8/5</i>

Edwin</pre>