2x means 2 × x
2x
2 × 3
6
x² means x × x
x²
3 × 3
9
At x = 3: 2x = 6 but x² = 9. Different things entirely — x² is bigger here.
Watch the gap. 2x doubles; x² squares. They only ever agree at x = 0 and x = 2. Slide into the negatives and see what squaring does to the sign.