# Question:Is there a underlying routine of showing that one geometric region which has been decribed implicitly (but not parametrically) is included in another?

## Question:Is there a underlying routine of showing that one geometric region which has been decribed implicitly (but not parametrically) is included in another?

Maple 2022

Let a, b, c, d be real numbers. Define two geometric regions implicitly: abcd＞0∧abacadbcbdcda2b2c2d2, and abcd＞0∧abcabdacdbcd＞0. Suppose that somebody wants to prove that the former region is a subset of the latter one. Can we implement such an implication simply using certain ready-made commands in basic Maple? In other words, it is hoped that

```restart;
RealDomain:-simplify(forall([a, b, c, d], a + b​​​​​​​ + c + d > 0 and a*b + a*c + a*d + b*c + b*d + c*d > a^2 + b^2 + c^2 + d^2 implies a*b*c*d > 0 and a*b*c + a*b*d + a*c*d + b*c*d > 0));```

Unfortunately, simplify just returns the statement unevaluated. So, how to address it in internal Maple?

Note. The desired result (or return value) is true (see below).

1. ```restart; # Do not with(Logic): here
RegularChains:-SemiAlgebraicSetTools:-QuantifierElimination(&A [d, c, b, a], ((d + c + b + a > 0) &and (b*a + c*a + d*a + c*b + d*b + d*c > a^2 + b^2 + c^2 + d^2)) &implies ((d*c*b*a > 0) &and (d*c*b + d*c*a + d*b*a + c*b*a > 0)));```
2. ```restart;
not SMTLIB:-Satisfiable(`not`(a + b + c + d > 0 and a*b + a*c + a*d + b*c + b*d + c*d > a^2 + b^2 + c^2 + d^2 implies d*c*b*a > 0 and a*b*c + a*b*d + a*c*d + b*c*d > 0)); # assuming real ```

​​​​​​​​​​​​​​​​​​​​​Either ⒈ or ⒉ needs external calls. It seems that the Maple standard library functions in List of Commands still fail in simplifying expressions in the aforementioned form. Am I right?

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