Question

How do you solve `p^2 - 4p + 4 = 0` using the quadratic formula?

Answer 1

The unique (double-root) in this case is `p=2`.

Explanation:

For an equation of the form `ax^2+bx+c`, the quadratic formula says the solutions are `x=(-b pm sqrt(b^2-4ac))/(2a)`. For this problem, `a=1`, `b=-4`, and `c=4`. Thus, there's just one answer:

`p=(4 pm sqrt(16-4*1*4))/(2*1)=(4 pm 0)/2=2`.