In the interval [0,2], take two numbers a and B randomly, then the probability of zero free function f (x) = x2 + ax + B2 is______ ．

In the interval [0,2], take two numbers a and B randomly, then the probability of zero free function f (x) = x2 + ax + B2 is______ ．

Take two numbers a and B randomly in the interval [0, 2], then the plane area corresponding to (a, b) is shown as the rectangle in the figure below: if the function f (x) = x2 + ax + B2 has no zero point, then a2-4b2 < 0, that is, the plane area corresponding to | a | and | 2B | is shown as the shadow in the figure below: ∵ s rectangle = 2 × 2 = 4S, shadow = 4-12 × 2 × 1 = 3 ∥ function f (?)