Which quadratic function has one real solution?

0 = 2 (x + 7) (x - 5)

0 = (x - 3) (x - 3)

0 = 2.4 (x - 2) (x + 2)

0 = (x - 2) (x - 1)

A quadratic equation could yield one of two types of roots: real and imaginary. Rational roots are whole numbers and fractions, whereas imaginary roots are complex numbers incorporating the 'i' symbol. When you say, the equation has one real root, this means that there are actually two roots but same in value. That would be letter (x-3) (x-3) = 0. Its root is x=3.