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Re: Radicals simplify

  • To: mathgroup at smc.vnet.net
  • Subject: [mg106438] Re: Radicals simplify
  • From: dh <dh at metrohm.com>
  • Date: Tue, 12 Jan 2010 05:16:24 -0500 (EST)
  • References: <hic37h$5ef$1@smc.vnet.net> <hieujs$mtu$1@smc.vnet.net> <higdis$ke6$1@smc.vnet.net>


Hi,

all these expressions have the same LeafCount. Therefore, the main rule 

is unsufficient to distinguish between this possibilities. There must be 

more (undocumented) rules to pick one. But it seems reasonable that 6 

Sqrt[2] is simplier than 3 Sqrt[8].

Daniel



francix wrote:

> "dh" <dh at metrohm.com> ha scritto nel messaggio 

> news:hieujs$mtu$1 at smc.vnet.net...

>>

>> Hi,

>>

>> why do you think x(x^2 y^3)^(1/4) is simpler than (x^6 y^3)^(1/4)?

>>

>> Mathematica needs some criterion for this decision. The default criterion is the

>>

>> "LeafCount[..]". If that does not suit you, you must define another

>>

>> criterion.

>>

>> Daniel

> 

> Thank you all for your answer.

> 

> I understand your explanations, but I have the impression

> that in this case Mathematica uses numbers in a different

> way from letters.

> 

> If I do

> Simplify[2 Sqrt[2] + 4 Sqrt[2]]  I get

> 

> 6 Sqrt[2]

> 

> or

> 

> Simplify[5 Sqrt[50] + 6 Sqrt[18]]  I get

> 

> 43 Sqrt[2]

> 

> Instead if I do

> 

> Simplify[5 x Sqrt[x] + 6 x Sqrt[x], x >= 0] or

> 

> Simplify[5 Sqrt[x^3] + 6 x Sqrt[x], x >= 0] I get

> 

> 11 x^(3/2)  instead of  11xSqrt[x]

> 

> As you know the last one is the result

> 

> normally found in Algebra books.

> 

> So, there is no solution?

> 

> 




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