Let f, g be measurable functions bounded on a set E of finite measurement. Show that: If f = a.e.g then ∫f = ∫g

Let f, g be measurable functions bounded on a set E of finite measurement. CA watch:

If f = a.e.g then ∫f = g on E

I have this proof of Cupta's book, but I do not understand how this step depends on what?

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