Posted by **Megan** on Friday, November 4, 2011 at 3:18pm.

Rationalize the denominator: 5 /4-squareroot 5

(five over four minus square root five)

Please explain

- Algebra -
**Steve**, Saturday, November 5, 2011 at 5:38pm
since (a-b)(a+b) = a^2 - b^2,

(4-sqrt(5))(4+sqrt(5) = 16-5 = 11

so, multiply top and bottom by 4+sqrt(5) to get

5(4+sqrt(5))/11 = (20 + 5sqrt(5))/11

- Algebra -
**Megan**, Saturday, November 5, 2011 at 10:00pm
Thank you so much!! It really helped me understand!

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