how would I write 4/√7 with a fraction whose denominator is even?

Thanks

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- Jul 25th 2011, 11:33 AMdrewmRadical fraction
how would I write 4/√7 with a fraction whose denominator is even?

Thanks - Jul 25th 2011, 11:40 AMPlatoRe: Radical fraction
- Jul 25th 2011, 11:57 AMdrewmRe: Radical fraction
ok thanks, but can you tell me how you got that?

- Jul 25th 2011, 12:01 PMPlatoRe: Radical fraction
- Jul 25th 2011, 12:04 PMe^(i*pi)Re: Radical fraction
If you think about it another way - you need to multiply top and bottom by $\displaystyle \sqrt{7}$ to rationalise the denominator. However, 7 is not an even number so you must multiply top and bottom by $\displaystyle 2$ since multiplying any integer by 2 gives an even number.

Plato did the same thing but combined the steps - Jul 25th 2011, 05:52 PMtheloserRe: Radical fraction
$\displaystyle \sqrt7\cdot\sqrt7=\sqrt{7\cdot7}=\sqrt{49}=7$

Like they said add 2 in front of the radical, there you would multiply $\displaystyle 7\cdot2$.