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Algebra Level 1

201 6 2 200 8 2 201 3 2 201 1 2 = ? \large \dfrac{\color{#D61F06}{2016^2}-\color{#3D99F6}{2008^2}}{\color{#D61F06}{2013^2}-\color{#3D99F6}{2011^2}} = \, ?

2016 None of the above 2 0 4

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3 solutions

Anish Harsha
Dec 9, 2015

201 6 2 200 8 2 201 3 2 201 1 2 \large \dfrac{\color{#D61F06}{2016^2-2008^2}}{\color{#3D99F6}{2013^2-2011^2}}

Using the algebraic identity, a 2 b 2 = ( a + b ) ( a b ) \color{#20A900}{a^2-b^2}=\color{#624F41}{(a+b)(a-b)} ,

= ( 2016 + 2008 ) ( 2016 2008 ) ( 2013 + 2011 ) ( 2013 2011 ) \large \dfrac{\color{#D61F06}{(2016+2008)(2016-2008)}}{\color{#3D99F6}{(2013+2011)(2013-2011)}}

= 4024 × 8 4024 × 2 \large \dfrac{\color{#D61F06}{4024 \times 8 }}{\color{#3D99F6}{4024 \times 2 }}

= 8 2 \large \dfrac{\color{#D61F06}{8}}{\color{#3D99F6}{2}}

= 4 \large \color{magenta}{4}

201 6 2 200 8 2 201 3 2 201 1 2 \Rightarrow \dfrac{2016^2-2008^2}{2013^2-2011^2}

Using the algebraic identity, a 2 b 2 = ( a + b ) ( a b ) a^2-b^2=(a+b)(a-b) ,

= ( 2016 + 2008 ) ( 2016 2008 ) ( 2013 + 2011 ) ( 2013 2011 ) \dfrac{(2016+2008)(2016-2008)}{(2013+2011)(2013-2011)}

= 4024 × 8 4024 × 2 \dfrac{4024 \times 8 }{4024 \times 2 }

= 4 \boxed{4}

Ahmed Obaiedallah
Dec 13, 2015

Let a = 2012 \Large a\normalsize =\color{maroon}{2012}

And substitute in the given expression

= ( a + 4 ) 2 ( a 4 ) 2 ( a + 1 ) 2 ( a 1 ) 2 = ( a 2 + 16 ) + 8 a ( a 2 + 16 ) + 8 a ( a 2 + 1 ) + 2 a ( a 2 + 1 ) + 2 a = 16 a 4 a = 4 =\dfrac{(a+4)^2-(a-4)^2}{(a+1)^2-(a-1)^2}=\dfrac{(\color{#D61F06}{a^2}+\color{#3D99F6}{16})+8a-(\color{#D61F06}{a^2}+\color{#3D99F6}{16})+8a}{\color{#D61F06}{(a^2}+\color{#3D99F6}{1})+2a-(\color{#D61F06}{a^2}+\color{#3D99F6}{1})+2a}=\dfrac{16a}{4a}=\color{magenta}{4}

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