Question

In black letters on white enamel. And on the jamb. A bit higher the number . Number 46 .what do you mean by
enamel and jamb ? what is 46?
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Answer 1

For a given x , if there exists x′ such that x + x′ ( = x′ + x ) = o , then x′ is called an additive inverse of x. x′ = x′ + o = x′ + (x + x″) = (x′ + x) + x″ = o + x″ = x″. For example, since addition of real numbers is associative, each real number has a unique additive inverse.