What Conditions Make a∘b Equal to b∘a for Given Functions?

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SUMMARY

The discussion focuses on the conditions under which the composition of two functions, defined as a=fx+g and b=hx+i, results in commutativity, specifically when a∘b equals b∘a. The derived expressions are a∘b(x)=fhx+gh+i and b∘a(x)=fhx+fi+g. To achieve equality, the coefficients and constants must satisfy the equations gh+i=fi+g, leading to specific relationships among the variables f, g, h, and i.

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Homework Statement


Let a=fx+g and b=hx+i. For which real numbers f,g,h,i a∘ b = b∘ a

Homework Equations





The Attempt at a Solution


a∘ b(x)=(a(b(x))= h(fx+g)+i= fhx+gh+i
b∘ a(x)=(b(a(x))= f(hx+i)+g= fhx+fi+g
I'm kind of stuck here as I don't think I know what the question is really asking for so I'm unable to proceed :S
 
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Equate the two, rearrange and find solutions, even if algebraic, for the unknowns you want. Just be careful because the question seems to be asking for the whole of the real numbers.

The Bob
 

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