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Unable to understand the theory mentioned

Screen Link:
https://app.dataquest.io/m/159/finding-extreme-points/2/introduction-to-derivatives

The below line is mentioned in the link above,
When x is less than 1.5, the slope is positive. As x approaches 1.5 from the left side, the slope decreases and approaches 0. At x=1.5, the slope of the tangent line is exactly 0.

But, what does it mean by x approaches 1.5 from the left side? does it mean x approaching 1.5 from 5 or 4 or does it mean x approaching 1.5 from the -1 or 0’s side?

In 2D, x is usually horizontal axis and y is vertical. Left means negative section of x number line. From left means from negative x to positive x direction.