Plss help i will give brainliest

Simplify (a/b - b/a) times (a - a^2/a+b) a - a^2/a=b is a mixed number

The position of a moving particle is given by the position function: f(t)=-9t-t^2-0.2t^3+0.1t^4 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)

The distance of a chord from the centre of a circle is 12cm and the lenght of the chord is 10cm. find the radius of the circle