$\"\"$

From the graph, let be the line: 1 passes through the points $\"\"$ .

Substitute the values of $\"\"$ in the slope formula $\"\"$ .

$\"\"$ .

From the graph, let be the line: 2 passes through the points $\"\"$ .

Substitute the values of $\"\"$ in the slope formula $\"\"$ .

$\"\"$ .

From the graph, let be the line: 3 passes through the points $\"\"$ .

Substitute the values of $\"\"$ in the slope formula $\"\"$ .

$\"\"$ .

Therefore slopes of line: 1, line: 2 and line: 3 are $\"\"$ respectively.

The line: 3 has a slope of $\"\"$ , the negative reciprocal of $\"\"$ , so the lines 2 and 3 are perpendicular. $\"\"$

The lines 2 and 3 are perpendicular.