Question: hgow to know the intersection of 2 functions

Hi let's say i have 2 functions the first one is f :=x->[[1, 0], [3, 3], [5, 3], [7, 0]]; the second one is g :=x->[[1, 0], [5, 4], [7, 4], [9, 0]]; when i use plot({f(x),g(x)}); i can see the both functions and the intersection but I don't know how to calculate the intersection Can you help me please thank you .
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