Two lines are perpendicular if and only if the product of their slopes are equal to -1. Consider the first equation. y=51x+1 Here, the slope is 51. This means that the slope m2 of any perpendicular line will satisfy the equation 51⋅m2=-1. To find this slope we'll multiply both sides by 5. m2=-5 We can see that in Ron-Jon's equation he wrote the slope 5, which is incorrect. The correct equation should be y=-5+6.