For all functions of the form f(x) = ax2 + bx + c, which is true when b = 0?

a. the graph will always have zero x-intercepts.
b. the function will always have a minimum.
c. the y-intercept will always be the vertex.
d. the axis of symmetry will always be positive.

The pyraminx is a rubik's cube-type toy in the shape of a tetrahedron. the pyraminx shown below has edges 15\,\text{cm}15cm long and vertical height h=12.2\,\text{cm}h=12.2cm. the triangle drawn with dashed lines is a right triangle. what is the distance rr? round your answer to the nearest tenth.