A linear function f(x) and its inverse f-1(x) intersect at the point (5,5). Create a function, f(x) that would satisfy this requirement
y = m x + b
inverse
x = m y + b
y = (x-b)/m
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5 = 5 m + b or 5 m = 5 - b
5 = (5-b)/m or 5 m = 5 - b
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5 m = 5 - b
if m = 1
5 = 5 + b and b = 0
5 = (5-b)and b = 0
so
f(x) = x should do
(that should have been obvious :)