Solve the problem.At time t ? 0, the velocity of a body moving along the s-axis is 
When is the body moving backward?
A. 1 < t < 9
B. t > 9
C. 0 ? t < 9
D. 0 ? t < 1
Answer: A
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Parametric equations and and a parameter interval for the motion of a particle in the xy-plane are given. Identify the particle's path by finding a Cartesian equation for it. Graph the Cartesian equation. Indicate the portion of the graph traced by the particle and the direction of motion.x = 49t2, y = 7t, -? ? t ? ?
A. y = x2; Entire parabola, left to right (from
2nd quadrant to origin to 1st quadrant)
B. y = x2; Entire parabola, right to left (from
1st quadrant to origin to 2nd quadrant)
C. x = y2; Entire parabola, bottom to top (from
4th quadrant to origin to 1st quadrant)
D. x = y2; Entire parabola, top to bottom (from
1st quadrant to origin to 4th quadrant)
Simplify the expression using the imaginary unit i.
A. -12i
B. 12
C. 12i
D. -12
Suppose a and b are real numbers other than zero and that 
. State whether the inequality is true or false.
?
?
A. False B. True
Perform the indicated operation. Write the answer in simplest form.20 ÷ 
A. 16
B. 15
C. 14
D. 