Question

$(0.4k^{3}-2.5k)-(2.4k^{3}+3k^{2}-1.2k)=LXB0\bigcirc -2.8k^{3}+3k^{2}-1.3kLXB1\bigcirc -2k^{3}+3k^{2}-3.7k$done

Explanation:

Step1: Distribute the negative sign

$(0.4k^3 - 2.5k) - 2.4k^3 - 3k^2 + 1.2k$

Step2: Combine $k^3$ terms

$0.4k^3 - 2.4k^3 = (0.4 - 2.4)k^3 = -2k^3$

Step3: Bring down the $k^2$ term

$-3k^2$

Step4: Combine $k$ terms

$-2.5k + 1.2k = (-2.5 + 1.2)k = -1.3k$

Step5: Combine all simplified terms

$-2k^3 - 3k^2 - 1.3k$

Answer:

-2k³ - 3k² - 1.3k (third option)