(2.4m²-0.8n²)×(0.8n²+2.4m²)

To simplify the expression, you can use the distributive property of multiplication:

(2.4m² - 0.8n²) × (0.8n² + 2.4m²)

Starting with the first term inside the parentheses:

(2.4m²) × (0.8n²) = 1.92m²n²

Next, multiply the first term inside the parentheses by the second term:

(2.4m²) × (2.4m²) = 5.76m^4

Now, move on to the second term inside the parentheses:

(-0.8n²) × (0.8n²) = -0.64n^4

Finally, multiply the second term inside the parentheses by the first term:

(-0.8n²) × (2.4m²) = -1.92m²n²

Combining these terms, you get:

(2.4m² - 0.8n²) × (0.8n² + 2.4m²) = 1.92m²n² + 5.76m^4 - 0.64n^4 - 1.92m²n²

Simplifying further:

1.92m²n² - 1.92m²n² + 5.76m^4 - 0.64n^4 = 5.76m^4 - 0.64n^4

Therefore, the simplified expression is 5.76m^4 - 0.64n^4.