One of the five quadratics below has a repeated root. (The other four have distinct roots.) What is the repeated root?
x^2 - 2x + 1
x^2 - 4x - 4
x^2 + 6x - 9
x^2 + 26x + 25
x^2 - 5x + 4
Double root occurs when discrimonant (b^2 - 4ac) of the quadratic equation = 0
First one: x^2 -2x +1
a = 1 b = -2 c = +1
( -2) ^2 - 4 (1)(1) = 0 ? yes =====> the first one has a double root