A parabola has a vertex at (0,0). The equation for the directrix of the parabola is x = –4. In which direction does the parabola open? up down right left.

The height of a triangle is 4 in. greater than twice its base. the area of the triangle is no more than 168 in.^2. which inequalitycan be used to find the possible lengths, x, of the base of the triangle?

Researchers were interested in whether relaxation training decreases the number of headaches a person experiences. they randomly assigned 20 participants to a control group or a relaxation training group and noted the change in number of headaches each group reported from the week before training to the week after training. which statistical analysis should be performed to answer the researchers' question?

Apublic library wants to place 4 magazines and 9 books on each display shelf. the expression 4s+9s represents the total number of items that will be displayed on s shelves. simplify the expression