       Re:Does anyone have an apparent fix for this mathematica problem?

• To: mathgroup at yoda.ncsa.uiuc.edu
• Subject: Re:Does anyone have an apparent fix for this mathematica problem?
• From: uunet!mathnx.byu.edu!smithw (William V. Smith)
• Date: Thu, 7 Jun 90 22:16:39 MDT

```Yes.  There is a fix.  It is available from your local friendly NeXT
Rep.  Here's what happens with the fix:

In:= InputForm[(b*c*(a + d - (a^2 + 4*b*c - 2*a*d + d^2)^(1/2))^3)/
(4*(a - d + (a^2 + 4*b*c - 2*a*d + d^2)^(1/2))*
(a^2 + 4*b*c - 2*a*d + d^2)^(1/2)) -
(b*c*(a +                 d + (a^2 + 4*b*c - 2*a*d + d^2)^(1/2))^
3)/
(4*(a - d                 - (a^2 + 4*b*c - 2*a*d + d^2)^(1/2))
*
(a^2 + 4*b        *c - 2*a*d + d^2)^(1/2))]

Out//InputForm=
(b*c*(a + d - (a^2 + 4*b*c - 2*a*d + d^2)^(1/2))^3)/
(4*(a^2 + 4*b*c - 2*a*d + d^2)^(1/2)*
(a - d + (a^2 + 4*b*c - 2*a*d + d^2)^(1/2))) -
(b*c*(a + d + (a^2 + 4*b*c - 2*a*d + d^2)^(1/2))^3)/
(4*(a^2 + 4*b*c - 2*a*d + d^2)^(1/2)*
(a - d - (a^2 + 4*b*c - 2*a*d + d^2)^(1/2)))

In:= rule={a->1,b->2,c->3,d->4}

Out= {a -> 1, b -> 2, c -> 3, d -> 4}

In:= N[res//.rule]

Out= res

In:= res=%1;

In:= N[res//.rule]

Out= 37.

In:= N[Together[Expand[res]]//.rule]

Out= 37.

In:= N[Simplify[res]//.rule]

Out= 37.

The bad result was from a known bug in the Together function
which is called by Simplify so both gave the wrong answer.

```

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