Plz help will give you brainliest if coorect Prove the sum of two rational numbers is rational where a, b, c, and d are integers and b and d cannot be zero.

Steps Reasons
1. a over b plus c over d Given
2. Multiply to get a common denominator
3. ad plus cb all over bd Simplify
Fill in the missing step in the proof.

Group of answer choices

ac over bd

ad over b plus cb over d

a plus c all over b plus d

ad over bd plus cb over bd

The position of a moving particle is given by the position function: f(t)=-9t-t^2-0.2t^3+0.1t^4 0 a. at what time does the particle reverse direction? b. when is the displacement positive? (round one decimal place and answer in interval notation) c. when is the displacement negative? (round one decimal place and answer in interval notation) d. when is the particle’s acceleration positive? (round one decimal place and answer in interval notation) e. when is the particle’s acceleration negative? (round one decimal place and answer in interval notation)