Parallel lines have the same slope. Because the functions \displaystyle f\left(x\right)=2x+3f(x)=2x+3 and \displaystyle j\left(x\right)=2x - 6j(x)=2x−6 each have a slope of 2, they represent parallel lines. Perpendicular lines have negative reciprocal slopes. Because −2 and \displaystyle \frac{1}{2}
2
1
are negative reciprocals, the equations, \displaystyle g\left(x\right)=\frac{1}{2}x - 4g(x)=
2
1
x−4 and \displaystyle h\left(x\right)=-2x+2h(x)=−2x+2 represent perpendicular lines.
