Solve x^2 +12x + 6 = 0 using the completing-the-square method.
a. x = negative six plus or minus the square root of thirty
b. x = six plus or minus the square root of thirty
c. x = negative six plus or minus the square root of six d. x = six plus or minus the square root of six

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.