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2 2009 2 2007 = ? \Large \color{#D61F06} 2^{\color{#69047E}{2009} } - \color{#D61F06} 2^{\color{#624F41}{2007}} = \ \color{#20A900}?

3 × 2 2007 3 \times 2^{2007} 2 2007 2^{2007} 2 2 2^2 2 × 2 2007 2 \times 2^{2007}

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17 solutions

Víctor Martín
Aug 20, 2014

Easy. As x m + n = x m x n { x }^{ m+n }={ x }^{ m }·{ x }^{ n } ,

2 2009 2 2007 = 2 2007 + 2 2 2007 = 2 2007 2 2 2 2007 { 2 }^{ 2009 }-{ 2 }^{ 2007 }={ 2 }^{ 2007+2 }-{ 2 }^{ 2007 }={ 2 }^{ 2007 }·{ 2 }^{ 2 }-{ 2 }^{ 2007 } .

Then, the result is:

2 2007 2 2 2 2007 = 2 2007 ( 2 2 1 ) = 2 2007 ( 4 1 ) = 3 2 2007 { 2 }^{ 2007 }·{ 2 }^{ 2 }-{ 2 }^{ 2007 }={ 2 }^{ 2007 }\left( { 2 }^{ 2 }-1 \right) ={ 2 }^{ 2007 }\left( 4-1 \right) =\boxed { 3·{ 2 }^{ 2007 } } .

x m + n x m + x n x^{m+n} \neq x^m + x^n . I think you meant to write x m + n = x m x n x^{m+n} = x^m \cdot x^n

Scott Mueller - 6 years, 9 months ago

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Oops. Sorry for the silly mistake. I've just fixed it.

Víctor Martín - 6 years, 9 months ago

Please don't write "easy". Even though the steps you used to get your solution are not as complex as the steps for a lot of other problems, the concept of subtracting values with exponents is much less intuitive than subtracting values without exponents. Nothing is so easy that everyone will be able to understand it immediately.

Andy Wong - 5 years, 3 months ago

Excellent solutions

Elavarasan Apple - 6 years, 9 months ago

excellent solution

braj singh - 6 years, 6 months ago

sir , where does 2^2-1 come from ?

Karl Anthony Baluyot - 6 years, 9 months ago

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I get it. thanks

Karl Anthony Baluyot - 6 years, 9 months ago

Oh, I did not thought of that.

Hon Ming Rou - 6 years, 9 months ago

excellent solution

padma vathi - 6 years, 9 months ago

Fantastic solution!

Olivia Ross - 6 years, 8 months ago

excellent answer

Saritha Sari - 6 years, 5 months ago

excellent solution

equation in first line is wrong....instead of + it should me *

Vishal Gupta - 6 years, 9 months ago

2^2007(2^2-1)=2^2007(4-1)=2^2007(3)

good answes of equation

dhruv dhasmana - 6 years, 9 months ago

good solution

Abdullah Khokhar - 6 years, 9 months ago
Roland Copino
Sep 15, 2014

This is my stupid solution..... Consider this.. If 2^4 - 2^2 = 12 , which is 3 x 2^2 , therefore it has the same scenarion with the original problem.. So , 2^2009 - 2^2007 = 3 x 2^2007 .. It is an easier solution for me.

  • scenario.. Sorry wrong spelling

Roland Copino - 6 years, 9 months ago
Parth Dwivedi
Sep 7, 2014

As we have to find,

2^2009 - 2^2007

=2^2007 (2^2 - 1) (taking 2^2007 common)

=2^2007 (4 - 1)

=2^2007 ( 3)

Thus giving us the answer,

=3×2^2007

Bob Dilworth
Feb 26, 2016

(2^2009) - (2^2007) = (2^2007x2x2) - (2^2007)

(2^2007x4) - (2^2007) = 2^2007x3

Mahtab Hossain
Apr 3, 2015

By taking common 2^2007 ,

2^2007 (2^2 - 1 ) = 3 * 2^2007

Gamal Sultan
Dec 22, 2014

2^2009 - 2^2007 = 4 X 2^2007 - 2^2007 = 2^2007 (4 - 1) = 3 X 2^2007

Roger Djedje
Dec 21, 2014

2^2009-2^2007=2^2007.2^2-2^2007----->2^2007(2^2-1)=3X2^2007

Anna Anant
Dec 21, 2014

2^2009 -2^2007 2^2007(2^2-2^0) 2^2009 -2^2007 3*2^2007

2^{2009}-2^{2007}=2^{2007+2}-2^{2007}=2^{2007}\times(2^2-1)=3\times2^{2007}.

Mohammed Radwan
Dec 20, 2014

=2^2009 - 2^2007 =2^2007(2^2 - 1 ) = 2^2007 × (4-1) = 2^2007 × (3) = 3 × 2^2007

Jagadeesh Alapati
Sep 27, 2014

2^2009-2^2007=2^2007(2^1-1)=2^2007(4-1)=3 . 2^2007

Jaswanth Varma
Sep 21, 2014

I think it would be rather easy if we take an example like this. 2 ^ 4 (-) 2 ^ 2 = 12 So 3 * 2 ^ 2 gives us the answer 12. So the final answer should be 3 * (2 ^ smaleer number) which is 3 * (2 ^ 2007).

Shashank Kris
Aug 31, 2014

this is a simple trick....if 2^x-2^(x-2)=3*2^(x-2)

Krishna Garg
Aug 22, 2014

We can write this as 2raise to power 20007( 2 square-1) that is 3 X 2 raise topower 2007 answer. K.K.GARG,India

Tamoghna Purkait
Aug 22, 2014

2^2009 - 2^2007 = 2^2007(2^2-1) = 3*2^2007

Let 2009 be a, then 2^a-2^a-2, then 2^a-1/4(2^a), after it is simplified an expression of 3(2^a-2) is formed. Consequently, the answer C suits the expression when it is substituited.

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