In 2015, there were about 22 million teenagers in the United States.
They each sent an average of 900 text messages per
month.
About how many text messages did all of the teenagers in
the United States send each month?
Express your answer using scientific notation.

Is there a direction u in which the rate of change of f(x,y)equals=x squared minus 3 xy plus 4 y squaredx2−3xy+4y2 at p(1,2) equals 14? give reasons for your answer. choose the correct answer below. a. no. the given rate of change is smaller than the minimum rate of change. b. no. the given rate of change is larger than the maximum rate of change. c. yes. the given rate of change is larger than the minimum rate of change and smaller than the maximum rate of change.