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Which microorganism responsible for bacteria? I'm trying to find a way to get my grades up in maths and I don't know how to focus on just studying does anyone know how to help? X^2-y^2=16? What's the first digit of Pi? Please help me with this math problem :) If f(g(x)) = g(f(x)) = x, and g(x) = 2 + ln(x+1), find f(4).?