Show that 0 ≤ e^−x2 ≤ e^−x for x ≥ 1 (Figure 12). Use the Comparison Test to show that ∫^∞₀ e^−x2 dx converges. It suffices (why?) to make the comparison for x ≥ 1 because 

-4 -3 -2 -1 1 y = elx -2 3 4