Why x becomes zero

The y-axis contains every point whose x-coordinate is zero. That is why substituting x=0x=0 reveals the y-intercept directly.

In standard form, the result is y= rac{C}{B} as long as Beq0B eq0.

When this is useful

  • Checking where a line starts on a graph.
  • Converting standard form to slope-intercept form.
  • Comparing two linear rules quickly without plotting many points.