Denestifying nested radicals

Algebra Level 2

3 + 3 + 2 + 3 + 7 + 48 = a + b \sqrt{3+\sqrt{3}+\sqrt{2+\sqrt{3}+\sqrt{7+\sqrt{48}}}} = a + \sqrt{b}

If a a and b b are positive integers, find a + b a + b .


The answer is 4.

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2 solutions

Rohit Udaiwal
Nov 1, 2015

First note that a + b + 2 a b = a + b \color{#3D99F6}{\sqrt{a+b+2\sqrt{ab}}=\sqrt{a}+\sqrt{b}} 3 + 3 + 2 + 3 + 7 + 48 = 3 + 3 + 2 + 3 + 4 + 3 + 2 12 = 3 + 3 + 2 + 3 + 4 + 3 = 3 + 3 + 4 + 2 3 = 3 + 3 + 3 + 1 = 4 + 2 3 = 3 + 1 2.732 \sqrt{3+\sqrt{3}+\sqrt{2+\sqrt{3}+\sqrt{7+\sqrt{48}}}} \ \\ =\sqrt{3+\sqrt{3}+\sqrt{2+\sqrt{3}+\color{#3D99F6}{\sqrt{4+3+2\sqrt{12}}}}} =\sqrt{3+\sqrt{3}+\sqrt{2+\sqrt{3}+\sqrt{4}+\sqrt{3}}} \\ =\sqrt{3+\sqrt{3}+\color{#3D99F6}{\sqrt{4+2\sqrt{3}}}}=\sqrt{3+\sqrt{3}+\sqrt{3}+1}=\color{#3D99F6}{\sqrt{4+2\sqrt{3}}}=\sqrt{3}+1 \approx 2.732

Nice use of the identity!

Sandeep Bhardwaj - 5 years, 3 months ago

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Thank you :)

Rohit Udaiwal - 5 years, 3 months ago

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Where does this identity come from? if there are other identities it would be nice if they had a wiki dedicated to them.

Hunter Seropian - 5 years, 2 months ago

Wow what a solution!!!!!!!!!!.

Megha Malyala - 4 years, 10 months ago

Nice work mate

shuddhabho nandi - 4 years, 10 months ago

Nice one dude

Kunal Bansal - 4 years, 10 months ago

They don't ask a+sqrt(b), they ask a+b! Nice solution!

Alfonso Vazquez Parcero - 4 years, 2 months ago

48 is missing on mobile,it's not fit at screen of mobile

Nikola Djuric - 4 years, 4 months ago

The question should say evaluate, not simplify.

Chad Brittle - 4 years, 3 months ago

No use of given identity in above

Prashant Kumar - 3 years, 11 months ago

Very creative solution

suzan khach - 3 years, 9 months ago

Great solution

Saksham Jain - 3 years, 6 months ago

Nice! I forgot that identity lol

Rohan Joshi - 6 months, 2 weeks ago

✓a + ✓b = 4

Am Kemplin - 1 month, 2 weeks ago

I got the same answer: 1 + 3^(1/2), 2.7321,27321 E-4,2.732...but none of the answers the system was accepting...Alas!

vinod trivedi - 4 years, 9 months ago

It is wrong. Because they asked to find 'a+b'. But you found "a+square root of b" .you did the problem correctly but you made a mistake at last. So, the answer is 3+1=4

Bhavana Netha - 4 years, 2 months ago
Esam Almohimmah
Apr 16, 2018

7 + 48 = 2 + 3 2 ( 2 + 3 ) = 1 + 3 4 + 2 3 = 1 + 3 \sqrt{7+\sqrt{48}} = 2+\sqrt{3} \\ \sqrt{2(2+\sqrt{3})} = 1+ \sqrt{3} \\ \sqrt{4+ 2\sqrt{3}} = 1+ \sqrt{3}

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