If sin(x) = 1/3 and sec(y) = 29/21, where x and y lie between 0 and /2, evaluate the expression. cos(x − y)

In a quadratic function of the form ax^2+bx+c, which of the following is not true? a. the y-intercept is c. b. if a is positive, the parabola opens up. c. the vertex has an x-coordinate of -b/2a. d. the axis of symmetry is the line y=-b/2a.