Where does the minus sign go when deriving the Stefan-Boltzmann Constant?

Question

When deriving the stefan boltzmann law from planks law. You may make a substitution (http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/stefan2.html). This substitution will lead to a stray minus sign in the equation. The rest of the derivation seems to just ignore the minus sign. Is there a reason for this?

user258881 · Answer

When you substitute
$$x=frac{hc}{lambda kT}$$
the limits of the integral also get reversed since
$$x=0iff lambdato inftyquadrm{and}quad xto infty ifflambda=0$$
Thus removing/cancelling the minus sign is completely justified.

Where does the minus sign go when deriving the Stefan-Boltzmann Constant?

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