Learn how to solve the quadratic equation x² – 11x + 28 = 0 using the quadratic formula. Clear explanation and calculation of roots. Therefore, the roots of the quadratic equation x² – 11x + 28 = 0 are 4 and 7. By following this step-by-step solution, you have successfully solved the quadratic equation x² – 11x + 28 = 0 using the quadratic formula.