Express 9 ten thousandths in scientific notation

What expression is equivalent to 1/2(2+3x-6)

Icould really use some with this question.

An object is accelerating at a constant rate. its velocity in feet per second as a function of time in seconds can be modeled by the linear function v(t) = 2.5t. what does the dependent variable represent for this function? a) acceleration b) distance c) slope d) velocity