(2.4m²-0.8n²)×(0.8n²+2.4m²)

To simplify the expression (2.4m²-0.8n²)×(0.8n²+2.4m²), we can use the FOIL method.

(2.4m² - 0.8n²) × (0.8n² + 2.4m²) = (2.4m² × 0.8n²) + (2.4m² × 2.4m²) + (-0.8n² × 0.8n²) + (-0.8n² × 2.4m²)

Now, let's simplify each term: (2.4m² × 0.8n²) = 1.92m²n² (2.4m² × 2.4m²) = 5.76m^4 (-0.8n² × 0.8n²) = -0.64n^4 (-0.8n² × 2.4m²) = -1.92m²n²

Putting it all together: 1.92m²n² + 5.76m^4 - 0.64n^4 - 1.92m²n²

Finally, combining like terms: (1.92m²n² - 1.92m²n²) + 5.76m^4 - 0.64n^4 = 0 + 5.76m^4 - 0.64n^4

The simplified expression is 5.76m^4 - 0.64n^4.