Maths year 11

Original post by z_o_e

What shall I do after?

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You should really stop asking so much step-by-step otherwise I'm the one doing the question for you. I mean what's the obvious thing to do when you have

2(3\sqrt5)+18

...?

Reply 1202

Original post by RDKGames

You should really stop asking so much step-by-step otherwise I'm the one doing the question for you. I mean what's the obvious thing to do when you have

2(3\sqrt5)+18

...?

Yeah it just I want to do one step by step with you so I can practise other questions on my own. I picked out the difficult ones. And I'm doing them but I get stuck.
Just got 2 left then ill stop

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Reply 1203

Original post by RDKGames

You should really stop asking so much step-by-step otherwise I'm the one doing the question for you. I mean what's the obvious thing to do when you have

2(3\sqrt5)+18

...?

I got 18 + 6 root 5

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Reply 1204

Original post by z_o_e

I got 18 + 6 root 5

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Yeppppp

Reply 1205

Original post by RDKGames

Yeppppp

Sorry if you're annoyed. But I never did a question like this before.

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Reply 1206

Original post by z_o_e

Sorry if you're annoyed. But I never did a question like this before.

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Correct. You know what root 4 is so you can replace that and you're done.

Reply 1207

Original post by RDKGames

Correct. You know what root 4 is so you can replace that and you're done.

So it's5 root 2 / 2?

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Reply 1208

Original post by z_o_e

So it's5 root 2 / 2?

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Yes

Reply 1209

Original post by RDKGames

Yes

Thank you

And I didn't understand this one .

Like I Multiplied it by a positive and negative surd.

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Reply 1210

Original post by z_o_e

Thank you

And I didn't understand this one .

Like I Multiplied it by a positive and negative surd.

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You don't understand it because you've done the method wrong. What you've done is assuming that

(a+b)(a+b)=a^2+b^2

which is plain wrong.

Multiply out the brackets.

Reply 1211

Original post by RDKGames

You don't understand it because you've done the method wrong. What you've done is assuming that

(a+b)(a+b)=a^2+b^2

which is plain wrong.

Multiply out the brackets.

What is this type of a question called I'll research a method.

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Reply 1212

Original post by z_o_e

What is this type of a question called I'll research a method.

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Just rationalising the denominator with 2 terms. http://www.mesacc.edu/~scotz47781/mat120/notes/rationalizing/two_terms/rationalize_denom_2_terms.html

Reply 1213

Original post by RDKGames

Just rationalising the denominator with 2 terms. http://www.mesacc.edu/~scotz47781/mat120/notes/rationalizing/two_terms/rationalize_denom_2_terms.html

How's this?

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Reply 1214

B_9710

Original post by z_o_e

How's this?

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Should be

\displaystyle \frac{2-\sqrt 3 }{2^2-(\sqrt 3)^2}

Reply 1215

Original post by B_9710

Should be

\displaystyle \frac{2-\sqrt 3 }{2^2-(\sqrt 3)^2}

What about now?

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Reply 1216

Original post by z_o_e

What about now?

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Why did you completely ignore the denominator the change?

Reply 1217

Original post by RDKGames

Why did you completely ignore the denominator the change?

What do you mean?

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Reply 1218

Original post by z_o_e

What do you mean?

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Denominator.

(2+\sqrt3)(2-\sqrt3)\not=2^2-(\sqrt2)^2

Reply 1219