Extraneous Root Lab
Graph y = √(ax+b) and y = c together: the intersection is the true solution — and squaring-only candidates that miss the curve are exposed as extraneous.
See the extraneous root miss
Set a, b for y = √(ax + b) (blue) and c for the line y = c (gold). Intersections are real solutions; the lab also shows what squaring alone would claim.