Rationalsing

[Pat_1211]

I been given this question to do and I have no idea. I want to cancel the root 2's but I dont see how they got the answer in the book.

It says rationalise

(3-SQRT(2))/(4+SQRT(2))

[RTagger]

multiply top and bottom by 4 + SQRT2

[KatieB]

Multiply top and bottom by (4-SQRT(2))

(3-SQRT(2))/(4+SQRT(2)) = (3-SQRT(2))*(4-SQRT(2)) / (4+SQRT(2))*(4-SQRT(2))

= (12-3root2 -4root2 + 2) / (16 -2)
= (14 - 5root2) / 14

[RTagger]

Multiply top and bottom by (4-SQRT(2))

Yep, thats what i meant ><

To rationalise, you need to get rid of surds on the denominator.