# simplifying a radical

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• October 22nd 2013, 03:42 PM
Jonroberts74
simplifying a radical
wolfram|alpha says this is false but doesnt

$\sqrt{36-4x^2} \Rightarrow 2\sqrt{9-x^2}$

trueq[sqrt(36-4x^2) equals 2 Sqrt[9 - x^2]] - Wolfram|Alpha
• October 22nd 2013, 04:02 PM
Plato
Re: simplifying a radical
Quote:

Originally Posted by Jonroberts74
wolfram|alpha says this is false but doesnt
$\sqrt{36-4x^2} \Rightarrow 2\sqrt{9-x^2}$
trueq[sqrt(36-4x^2) equals 2 Sqrt[9 - x^2]] - Wolfram|Alpha

On the other hand, look at this.
• October 22nd 2013, 04:06 PM
emakarov
Re: simplifying a radical
And this.
• October 22nd 2013, 04:07 PM
Jonroberts74
Re: simplifying a radical
why would it state it as false? Because, something subtracting something it equals is zero.
• October 22nd 2013, 04:41 PM
topsquark
Re: simplifying a radical
And yet again. Obviously "trueq" is a bit titchy. Always trust your mind over a computer.

-Dan
• October 22nd 2013, 04:44 PM
Plato
Re: simplifying a radical
Quote:

Originally Posted by Jonroberts74
why would it state it as false? Because, something subtracting something it equals is zero.

Because no computer algebra system is flawless.
You may be miss-using the "is equal" operation. Although, I have never seen that operation. So I have no idea how to answer your doubt.