What is the slope of a line perpendicular to the line in this graph?

Question

anonymous · Answer

click

anonymous · Answer

is it the blue line

anonymous · Answer

it should be no slope if it is the blue line

anonymous · Answer

Draw a line perpendicular to the blue line. It's slope will give you your answer.

anonymous · Answer

The slope is the change in y over the change in x.  Choose any two points on the blue line.  The change in y is some real number.  The change in x is zero.  Division by zero is undefined, so there is no slope.  

Pick a convenient line perpendicular to the blue line, like the x-axis.  Choose any two points.  The change in y will be zero.  The change in x will be some real number. 0/any real number is zero.  The slope of the perpendicular line is zero.