# a level binomials

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https://prnt.sc/up26kj

please help. i dont care about the working out. just need answers to check against my teachers solutions which i think is wrong

please help. i dont care about the working out. just need answers to check against my teachers solutions which i think is wrong

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#2

(Original post by

https://prnt.sc/up26kj

please help. i dont care about the working out. just need answers to check against my teachers solutions which i think is wrong

**a_level185**)https://prnt.sc/up26kj

please help. i dont care about the working out. just need answers to check against my teachers solutions which i think is wrong

Last edited by mqb2766; 3 weeks ago

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(Original post by

What was your teachers solutions? Why do you think they're wrong?

**mqb2766**)What was your teachers solutions? Why do you think they're wrong?

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#4

True, 0.95 is a bad estimate for 79/300 root 3 but without the your working, no-one here can help you.

Last edited by nerak99; 3 weeks ago

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(Original post by

True, 0.95 is a bad estimate for 79/300 root 3 but without the your working, no-one here can help you.

**nerak99**)True, 0.95 is a bad estimate for 79/300 root 3 but without the your working, no-one here can help you.

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#6

(Original post by

I would much rather do someone’s question than go through their long tideous working out

**a_level185**)I would much rather do someone’s question than go through their long tideous working out

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okay i will. so you agree with my teacher?

(Original post by

Why not post your attempt then? I got close to .95 for the first three x terms (up to and including cubic).

**mqb2766**)Why not post your attempt then? I got close to .95 for the first three x terms (up to and including cubic).

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#8

(Original post by

okay i will. so you agree with my teacher?

**a_level185**)okay i will. so you agree with my teacher?

Last edited by mqb2766; 3 weeks ago

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(Original post by

I don't really know what you've / your teacher has done so not sure who I agree with. Note the 0.95 is just from the series expansion with the sqrt(3) removed and x=3/40., I.e. It's sqrt(0.9).

**mqb2766**)I don't really know what you've / your teacher has done so not sure who I agree with. Note the 0.95 is just from the series expansion with the sqrt(3) removed and x=3/40., I.e. It's sqrt(0.9).

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#10

(Original post by

Is there a way you can upload a picture please? I’m a visual learner and reading this looks alien to me

**a_level185**)Is there a way you can upload a picture please? I’m a visual learner and reading this looks alien to me

Happy to help you with what you've done.

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https://prnt.sc/upgafu

im not the type of guy to expect others to do my homework for me. this isnt even my homework, it's past paper questions for my revision and i've tried relentlessly to get the answer but im out of hope.

i hope you can make sense of my work. i have tried to do it step by step

im not the type of guy to expect others to do my homework for me. this isnt even my homework, it's past paper questions for my revision and i've tried relentlessly to get the answer but im out of hope.

i hope you can make sense of my work. i have tried to do it step by step

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#12

(Original post by

https://prnt.sc/upgafu

im not the type of guy to expect others to do my homework for me. this isnt even my homework, it's past paper questions for my revision and i've tried relentlessly to get the answer but im out of hope.

i hope you can make sense of my work. i have tried to do it step by step

**a_level185**)https://prnt.sc/upgafu

im not the type of guy to expect others to do my homework for me. this isnt even my homework, it's past paper questions for my revision and i've tried relentlessly to get the answer but im out of hope.

i hope you can make sense of my work. i have tried to do it step by step

It's almost like there's an unnecessary sqrt (3) kicking around?

Last edited by mqb2766; 3 weeks ago

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(Original post by

The series expansion part looks good, 759/800 which is sqrt(0.9) or 3/sqrt(10).

It's almost like there's an unnecessary sqrt (3) kicking around?

**mqb2766**)The series expansion part looks good, 759/800 which is sqrt(0.9) or 3/sqrt(10).

It's almost like there's an unnecessary sqrt (3) kicking around?

im so confused, i did the other expansion and i got the same answer.... what do you mean by a square root hanging around?

i needed to multiply by 1/root 3 to get from 3root30/10 to 3/root 10 as the question asks.

oh wait i know what you mean about the root3. the question asks in the form kroot3. i dont know how to do that. so i thought id bring a root 3 out. but then k isnt a rational number

Last edited by a_level185; 3 weeks ago

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#14

(Original post by

https://prnt.sc/upgomb

im so confused, i did the other expansion and i got the same answer...

**a_level185**)https://prnt.sc/upgomb

im so confused, i did the other expansion and i got the same answer...

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(Original post by

In your working you want to approximate 3sqrt(30)/10? Is that right?

**mqb2766**)In your working you want to approximate 3sqrt(30)/10? Is that right?

thats how you get from 3root30/10 to 3/root10

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(Original post by

In your working you want to approximate 3sqrt(30)/10? Is that right?

**mqb2766**)In your working you want to approximate 3sqrt(30)/10? Is that right?

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#17

(Original post by

yes. i expanded (3-4x)^1/2 . then when i sub in the given x value 3/40 , i get the approximation for 3sqrt(30)/10. so to find 3/root10, i multiplied everything by 1/root3.

thats how you get from 3root30/10 to 3/root10

**a_level185**)yes. i expanded (3-4x)^1/2 . then when i sub in the given x value 3/40 , i get the approximation for 3sqrt(30)/10. so to find 3/root10, i multiplied everything by 1/root3.

thats how you get from 3root30/10 to 3/root10

3/sqrt(10) = sqrt(9/10) = 759/800

3sqrt(30)/10 = sqrt(3) sqrt(9/10) = 759/800 sqrt(3)

3sqrt(30)/10 = 3sqrt(3)/sqrt(10)

Pick whichever answer is correct for the question.

Last edited by mqb2766; 3 weeks ago

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#18

there does not seem to be a √3 in the answer... it looks like the question is wrong.

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if k is 759/800 then thats like saying 3/root10 is (759/800)*root3. which is the estimation for (3root30)/10. not the estimation for 3/root10.

to get from (3root30)/10 to 3/root10, i need to multiply by 1/root3.

so then that is (759/800)*root3) multiplied by (1/root3.). so the root3 cancels out and the final answer is just 759/800. which isnt in terms of root 3.

and when you do 3/40 you get 0.94868. and 759/800 is o.94875. so that means that is the correct estimation because it's so close. But literally no way of making it in terms of root 3

to get from (3root30)/10 to 3/root10, i need to multiply by 1/root3.

so then that is (759/800)*root3) multiplied by (1/root3.). so the root3 cancels out and the final answer is just 759/800. which isnt in terms of root 3.

and when you do 3/40 you get 0.94868. and 759/800 is o.94875. so that means that is the correct estimation because it's so close. But literally no way of making it in terms of root 3

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#20

(Original post by

if k is 759/800 then thats like saying 3/root10 is (759/800)*root3. which is the estimation for (3root30)/10. not the estimation for 3/root10.

to get from (3root30)/10 to 3/root10, i need to multiply by 1/root3.

so then that is (759/800)*root3) multiplied by (1/root3.). so the root3 cancels out and the final answer is just 759/800. which isnt in terms of root 3.

and when you do 3/40 you get 0.94868. and 759/800 is o.94875. so that means that is the correct estimation because it's so close. But literally no way of making it in terms of root 3

**a_level185**)if k is 759/800 then thats like saying 3/root10 is (759/800)*root3. which is the estimation for (3root30)/10. not the estimation for 3/root10.

to get from (3root30)/10 to 3/root10, i need to multiply by 1/root3.

so then that is (759/800)*root3) multiplied by (1/root3.). so the root3 cancels out and the final answer is just 759/800. which isnt in terms of root 3.

and when you do 3/40 you get 0.94868. and 759/800 is o.94875. so that means that is the correct estimation because it's so close. But literally no way of making it in terms of root 3

3/sqrt(10) = 759/800.

3 sqrt(3)/sqrt(10) = 3 sqrt(30/10 = 759/800 sqrt(3)

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