[color=#000000]Lines a and b now form a 90 degree angle between them. What can you say about their slopes?[/color]
[b]Their slopes are inverse reciprocals of each other.[/b] ( [math]\frac{a}{b}[/math]is the reciprocal of [math]\frac{b}{a}[/math])Inverse means opposite, so negative sign. In other words, when you multiply the slopes together, you get -1.