radical expression and simplifying

[Ty]

I am new and have a question, and probably more to come. Here is the first one: how do I write an expression in radical form?
Example: (8x^5y^2)^7/5--
When I put this in as it stands I get this:
2^21/5x^7y^14/5
What I need is something like this: 5 square root sign(8s^5y^2)^7.


Second:
Simplify 5^square root sign (288x^3y^21)
I get this: 2*3^2/5*x^3/5*y^21/5
I need: 2y^5 (5) root sign (9x^3y^6)

If I had a square root sign on my keyboard it would be easier to show.

Any help would be appreciated.

[mellamokb]

Hi Ty,

Welcome to TI-89 Forums!

First, I am wondering why you care what the output looks like? If you just want the same thing as what you put in, and nothing simplified or evaluated, you can do that on paper. The calculator tends to simplify everything under its own terms of simplification, so making simplification on a complicated expression is best done by hand if you want to "see the steps" and if you're not going to "plug" in some values of x and y, for instance.

Otherwise, the "Root(" function can take two arguments, where the first argument is the expression under the radical and the second argument is the n in "nth root". However, this only causes the "pretty print" engine to display the root on the left side (the entry column), but the output expression is still the simplified "2^21/5x^7y^14/5". Like I've said before, the purpose of the AMS software engine in the calculator is to manipulate the variables, not display them in the most "convenient" or "efficient" manner. Only a human can understand the best "representation" for a given expression, because the calculator has to convert it to its "lowest terms" for most efficient calculation. As another example, if you do anything with trigonometric identities, the result will always be in terms of "Sin(" and "Cos(", whereas a human might see fit to use "Tan(" to represent something well. That's because the calculator can do the math, but it can't understand the most "elegant" representation like a human can in not simplifying something that doesn't make sense to simplify, like a "Sec(" or a fifth root.

I hope this makes sense. Please reply with any more questions, and I will do the best I can to help you. This isn't a very active forum right now.

~ mellamokb

[Ty]

[mellamokb]

Hi Ty,

The only thing I don't understand: if you put something in the calculator to get it back out in the same format, what are you trying to accomplish? You are just getting the same thing back out that you put in, nothing has changed. Do you have an example of a problem you have tried to solve, where you put something in and didn't get back out what you wanted--and some processing or computation was involved?

Thank you,

~ mellamokb

[Ty]

[mellamokb]

Ty,

Your calculator cannot do this because your notion of simplified is different from the calculator's. If it must be simplified a certain way for the class, then I would suggest learning that method so you can do that conversion by hand. That is probably the purpose of the problem on the test--to check your ability to manipulate roots manually. These things don't take a "math wiz" to understand, just a little practice.

Sorry to disappoint you

~ mellamokb