What is the length of bc?

bc=

How to use order of operation in 20 divide by 4 multiply 5 = 1

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)

I'm a polygon i have no parallel lines i am formed 3 line segments i have one right angle two of my angles are angles what am i