Observe the graph.

Slope of a tangent line with points  and  : .

Consider two points on the tangent line passing through the point .

The points on the tangent line are   and .

Slope of the tangent line: .

The slope of the tangent line at  is .

Consider two points on the tangent line passing through the point .

The points on the tangent line are  and 

Slope of the tangent line: .

The slope of the tangent line at  is .

The slope of the tangent line at  is .

The slope of the tangent line at  is .