x^2 + 2x + 7 is a quadratic equation. The discriminant, D=b^2-4ac, determines the type and number of solutions to a quadratic. Where ‘a’ is the coefficient of x^2, ‘b’ is the coefficient of x and c is the constant term in the quadratic. In this quadratic equation a=1, b=2 and c=7. Therefore D=2^2-4(1)(7) = -20. When the discriminant is negative there are no real solutions only imaginary solutions.
