Simplifying Cubic

Level 1

What do we get after simplifying:

x 6 y 6 ( x 4 + x 2 y 2 + y 4 ) ( x y ) \dfrac{x^6- y^6}{(x^4 + x^2y^2 + y^4)(x-y)}


Inspiration: Real Algebra 2

x 3 + y 3 x^3 + y^3 x y x - y x 2 + y 2 x^2 + y^2 x + y x + y

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3 solutions

Mahdi Raza
May 24, 2020

Let a = x 2 a = x^2 and b = y 2 b = y^2

x 6 y 6 ( x 4 + x 2 y 2 + y 4 ) ( x y ) = a 3 b 3 ( a 2 + a b + b 2 ) ( x y ) = ( a b ) ( a 2 + a b + b 2 ) ( a 2 + a b + b 2 ) ( x y ) = x 2 y 2 x y = ( x + y ) ( x y ) x y = x + y \dfrac{x^6- y^6}{(x^4 + x^2y^2 + y^4)(x-y)} = \dfrac{a^3- b^3}{(a^2 + ab + b^2)(x-y)} = \dfrac{(a - b)(a^2 + ab + b^2)}{(a^2 + ab + b^2)(x-y)} = \dfrac{x^2 - y^2}{x - y} = \dfrac{(x+y)(\cancel{x-y})}{\cancel{x-y}} = \boxed {x+y}

Thanks for recommending my problem this is also a very nice one

Joshua Olayanju - 1 year ago

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You're welcome, that problem was nice as well

Mahdi Raza - 1 year ago

I used the same solution

Joshua Olayanju - 1 year ago

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Well done!!

Mahdi Raza - 1 year ago

Have you tried Real Algebra (1)?

Joshua Olayanju - 1 year ago

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I don't remember, do you have it's link?

Mahdi Raza - 1 year ago

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https://brilliant.org/problems/real-algebra/?ref_id=1590610

Joshua Olayanju - 1 year ago

Nice problem! By the way, how do you cancel terms in LaTeX? Thanks!

Vinayak Srivastava - 1 year ago

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use \cancel{} and \bcancel{}

Mahdi Raza - 1 year ago

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OK. Thanks!

Vinayak Srivastava - 1 year ago

hey,mahdi please state that the x =!y

Chew-Seong Cheong
May 24, 2020

x 6 y 6 ( x 4 + x 2 y 2 + y 4 ) ( x y ) = ( x 3 y 3 ) ( x 3 + y 3 ) ( ( x 2 + y 2 ) 2 x 2 y 2 ) ( x y ) = ( x y ) ( x 2 + x y + y 2 ) ( x + y ) ( x 2 x y + y 2 ) ( x 2 + x y + y 2 ) ( x 2 x y + y 2 ) ( x y ) = x + y \begin{aligned} \frac {x^6-y^6}{(x^4+x^2y^2 + y^4)(x-y)} & = \frac {(x^3-y^3)(x^3+y^3)}{((x^2+y^2)^2 - x^2y^2)(x-y)} = \frac {\cancel{(x-y)}\cancel{(x^2+xy+y^2)}(x+y)\cancel{(x^2-xy+y^2)}}{\cancel{(x^2+xy+y^2)}\cancel{(x^2-xy+y^2)}\cancel{(x-y)}} = \boxed{x+y} \end{aligned}

I think you have a typo in the numerator of the first term. It’s x 6 y 6 x^6-y^6

Mahdi Raza - 1 year ago

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Thanks, I have amended it

Chew-Seong Cheong - 1 year ago

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Great, you’re welcome!

Mahdi Raza - 1 year ago

Multiply and divide by x+y we will directly get x+y

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