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Algebra Level 1

3 967 3 965 + 16 3 965 + 2 = ? \large \frac {3^{967} - 3^{965} + 16}{3^{965} + 2 } = \ ?


The answer is 8.

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7 solutions

Alex Delhumeau
Jun 3, 2015

3 967 3 965 + 16 3 965 + 2 = 9 ( 3 965 ) 3 965 + 16 3 965 + 2 = 8 ( 3 965 + 2 ) 3 965 + 2 \LARGE{\frac{3^{967}-3^{965}+16}{3^{965}+2}=\frac{9(3^{965})-3^{965}+16}{3^{965}+2}=\frac{8(3^{965}+2)}{3^{965}+2}}

= 8 . =\large{\boxed{8}}.

Moderator note:

A nice standard approach.

Bonus question : Prove that 3 965 + 2 3^{965} + 2 is a composite number. And prove that it has at least 2 distinct prime factors.

3 965 3^{965} must end in a 3 3 , because 3 ( 4 n 3 ) 3^{(4n - 3)} will always end in a 3 3 . Therefore, 3 965 + 2 3^{965} + 2 must end in a 5 5 .

Numbers that end in 5 5 but are not equal in 5 5 will always be composite. Since 3 965 + 2 3^{965} + 2 divided by 5 5 will not equal 5 5 or any power of 5 5 , it must have at least 2 2 distinct prime factors.

Ashwin Padaki - 6 years ago

Great solution!!! Factoring out is always good when dealing with large exponents...

Ashwin Padaki - 6 years ago

Dint get it! Explain in other easier way if possible! Please!

Om Pandya - 5 years, 11 months ago
Jack Rawlin
Dec 31, 2015

Let x = 3 395 x = 3^{395} , 9 x = 3 397 9x = 3^{397}

3 967 3 965 + 16 3 965 + 2 9 x x + 16 x + 2 \frac{3^{967} - 3^{965} + 16}{3^{965} + 2} \Rightarrow \frac{9x - x + 16}{x + 2}

9 x x + 16 x + 2 = 8 x + 16 x + 2 = 8 ( x + 2 ) x + 2 \frac{9x - x + 16}{x + 2} = \frac{8x + 16}{x + 2} = \frac{8(x + 2)}{x + 2}

8 ( x + 2 ) x + 2 = 8 x + 2 x + 2 = 8 1 \frac{8(x + 2)}{x + 2} = 8 \cdot \frac{x + 2}{x + 2} = 8 \cdot 1

3 967 3 965 + 16 3 965 + 2 = 8 \Large \boxed{\frac{3^{967} - 3^{965} + 16}{3^{965} + 2} = 8}

Anaghjyoti Ghosh
Jun 4, 2015

[3^965(9-1)+16]/3^965+2 =[3^965*8+16]/3^965+2 =8(3^965+2)/3^965+2 =8

Your LaTeX \LaTeX editing is not very good.

Ashwin Padaki - 6 years ago

tx Anaghjyoti Ghosh

If you want to learn real LaTeX \LaTeX , read this

Ashwin Padaki - 6 years ago

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Thanks for providing the LATEX site, expecting more related to above & other use-full math web sites

azadali jivani - 5 years, 8 months ago

3 965 × ( 9 1 ) + 16 3 965 + 2 = 8 ( 3 965 + 2 ) 3 965 + 2 = \dfrac{3^{965}\times(9-1) + 16}{3^{965}+2} = \dfrac{8(3^{965} +2)}{3^{965}+2} = 8 \boxed {8}

Rishik Jain - 5 years, 5 months ago

really thanx the solution provided up is not much clear but for this no words but no.s

Sàháj Siñgh - 6 years ago
Siva Ramakrishnan
Dec 31, 2015

3^965 (9-1)+ 16÷3^965+2

3^965(8)+ (8)2÷3^965 3^965+2 cancel with each other and the answer is 8

Gustavo Milla
Jul 30, 2015

excellent solution

Abhaya Vinayak - 5 years, 5 months ago
Shazid Reaj
Jun 26, 2015

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