Problem
ALG-B1-M03-P010 One Real Root
#10
★★☆☆☆ Level 2 of 5
For which \(a\) does \(x^2-4x+a=0\) have exactly one real root?
A quadratic equation has exactly one real root when its discriminant is zero.
The discriminant is \(D=16-4a\). We need \(D=0\), so \(16-4a=0\).
Thus \(a=4\).
The parameter is connected to tangency with the axis.