Why does the distributive property fail when comparing expressions?

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Stephen Prunty
Stephen Prunty 2018-4-18
回答： Star Strider 2018-4-18
As a simplified example, I'm trying to compare whether two expressions are equal, where they are simply written differently. But
syms a x y;
logical((x+y)*a == x*a + y*a)
returns false, and everything else that assumes distributivity of + and *. Is there some other function that will help me, or some explanation why this happens?

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回答（1 个）

Star Strider
Star Strider 2018-4-18

To get logical results with symbolic expressions, use the isAlways (link) function.

syms a x y;
TF = isAlways((x+y)*a == x*a + y*a)

TF =

    logical
     1

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