The sum of two numbers is 13. two times the first number minus three times the second number is one. if you let x stand for the first number and y for the second number what are the two numbers?

and !

7x+8y=-18, 4x-9y=-3 solve the system of equations

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 standard deviation for a set of data is 5.5. the mean is 265. what is the margin of error?