This is due today please help me

What’s the numerical coefficient of 6xy

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)

Julie multiplies 6.27 by 7 and claims the product is 438.9 .explain without multiplying how you know juliesanswer is not correct.find the correct answer