The discriminate is 100-4(25)=0 That means just one real root, or you can say it repeats, so you get the same real root twice. When the discriminate = 0 that's what happens.
The discriminate is b2-4ac. With this quadratic equation b=-10, a=1 c=25
Graph it and it just touches the x-axis once. It's a parabola with its vertex touching the x-axis
Factor the equation y=(x-5)2 That's two factors (x-5) and (x-5). Set each = 0, solve for x. x=5 and 5 again.
The point (5,0) is the parabola's vertex, it's minimum point, the only place the parabola touches the x-axis
5 is the real root, or zero. It repeats once. 5 and 5, as quadratic equations always have 2 roots, sometimes 2 real, sometimes 1 real that repeats, , sometimes 2 imaginary roots. That corresponds to a parabola intersecting the x-axis twice, once or never.