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Slope of parallel and perpendicular lines

Parallel lines have the same slope.
Perpendicular lines have slopes that are opposite reciprocals, like $\frac{a}{b}$ and $-\frac{b}{a}$. The slopes also have a product of -1.

Line t has a slope of $\frac{5}{8}$. Line u has a slope of $-\frac{8}{5}$ . Are line t and line u parallel or perpendicular?

The lines are not parallel because $\frac{5}{8}$ and $-\frac{8}{5}$ are not equal.

The lines are perpendicular because $\frac{5}{8}$ and $-\frac{8}{5}$ are opposite reciprocal:

 $\frac{5}{8}$ Take the slope of line t $\frac{8}{5}$ Find the reciprocal $-\frac{8}{5}$ Find the opposite

 Yes, $\frac{5}{8}$ and $-\frac{8}{5}$ are opposite reciprocals.

So, the lines are perpendicular.

Line i has a slope of $\frac{3}{2}$. Line u has a slope of $\frac{3}{2}$. Are line i and u parallel or perpendicular?
parallel
perpendicular
neither