The Roots of a Quadratic Equation

Read the coefficients a, b, and c of ax^2 + bx + c = 0 as real numbers and print its roots. If a is zero (within a tolerance of 1e-9), print not a quadratic equation and return 1. Otherwise compute the discriminant d = b*b - 4ac and use an if, else if, else ladder with the same tolerance: when d is greater than 1e-9 print roots are real and distinct, then root1 = (-b + sqrt(d)) / 2a and root2 = (-b - sqrt(d)) / 2a on two lines; when d is within 1e-9 of zero print roots are real and equal, then root = -b / 2a; otherwise print roots are complex, then root1 = real + imagi and root2 = real - imagi, where real = -b / 2a and imag = sqrt(-d) / |2a|, so that imag is always positive and the sign printed between the parts is the sign of the root. Every value is printed to two decimal places in the forms root1 = 3.00, root = -1.00, root1 = -0.50 + 0.87i, and root2 = -0.50 - 0.87i. If the three numbers cannot be read, print invalid input and return 1.