(1.7s+0.3t²)×(0.3t²-1.7s)

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

(1.7s + 0.3t²)×(0.3t² - 1.7s) = 1.7s × 0.3t² - 1.7s × 1.7s + 0.3t² × 0.3t² - 0.3t² × 1.7s

Now let's simplify each term:

1.7s × 0.3t² = 0.51s t² -1.7s × 1.7s = -2.89s² 0.3t² × 0.3t² = 0.09t⁴ 0.3t² × 1.7s = 0.51s t²

Putting it all together:

0.51s t² - 2.89s² + 0.09t⁴ + 0.51s t²

= 1.02s t² - 2.89s² + 0.09t⁴