(1.3x³-1.8y²)×(1.8y²+1.3x³)

To simplify the expression (1.3x³ - 1.8y²) × (1.8y² + 1.3x³), we can use the FOIL method.

FOIL Method: F - Multiply the first terms of each binomial. O - Multiply the outer terms of each binomial. I - Multiply the inner terms of each binomial. L - Multiply the last terms of each binomial.

(1.3x³ - 1.8y²) × (1.8y² + 1.3x³) = (1.3x³ × 1.8y²) + (1.3x³ × 1.3x³) + (-1.8y² × 1.8y²) + (-1.8y² × 1.3x³)

Simplifying the expression, we get: 2.34x³y² + 1.69x⁶ - 3.24y⁴ - 2.34x³y²

Now we can combine like terms: 2.34x³y² - 2.34x³y² + 1.69x⁶ - 3.24y⁴

The final simplified expression is: 1.69x⁶ - 3.24y⁴