Question 995311
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In slope-intercept form:
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{{{y=mx+b}}}
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m is the slope. 
To compare lines: 
If m's are equal and b's are not, lines are parallel.
If m's and b's are both equal, lines are the same.
If m in equation 2 equals -1/m from equation 1, lines are perpendicular.
Equation 1: y=5x+6 . m=5; b=6
1. y=-5x-6 m=-5 . . Neither parallel nor perpendicular
2. y=6 m=0 . . Neither parallel nor perpendicular
3. y-15=5(x-8)
. . y=5x-25 m=5; b=-25 . . Parallel    
4. y=5x+8 m=5;b=8 . . Parallel
5. y=1/5x-15 m=1/5 . . Neither parallel nor perpendicular
6. y=-1/5x+3 m=-1/5 . . Perpendicular
7. x+5y=30 
. . 5y=-x+30
. . y=(-1/5)x+6 m=-1/5 . . Perpendicular 
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