A quadratic equation has only one distinct solution when the discriminant is zero or when it factors into a perfect square trinomial.
Let's analyze each of the given equations:
-
\(x^2 - 5x + 4 = 0\)
Factors to \((x - 1)(x - 4) = 0\)
Solutions: \(x = 1\) and \(x = 4\) (two distinct solutions) -
\(x^2 + 4x + 4 = 0\)
Factors to \((x + 2)(x + 2) = 0\)
Solution: \(x = -2\) (one distinct solution) -
\(x^2 - 4 = 0\)
Factors to \((x - 2)(x + 2) = 0\)
Solutions: \(x = 2\) and \(x = -2\) (two distinct solutions) -
\(x^2 + 5x + 4 = 0\)
Factors to \((x + 1)(x + 4) = 0\)
Solutions: \(x = -1\) and \(x = -4\) (two distinct solutions)
From this analysis, the equation that has only one distinct solution is:
\(x^2 + 4x + 4 = 0\).