An algebra problem by Swastik Sahoo

Algebra Level 3

If x = 2 + 2 1 / 3 + 2 2 / 3 x=2+2^{1/3}+2^{2/3} , find the value of x 3 6 x 2 + 6 x 2 x^3 - 6x^2 +6x -2 .


The answer is 0.

This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try refreshing the page, (b) enabling javascript if it is disabled on your browser and, finally, (c) loading the non-javascript version of this page . We're sorry about the hassle.

2 solutions

Praguna Manvi
Sep 25, 2015

x=2+2^1/3+2^2/3

bringing 2 on L.H.S and cubing on b.s

(x-2)^3=(2^1/3+2^2/3)^3

expanding.......... x^3-8-6x(x-2)=2+4+6(2^1/3+2^2/3)

but 2^1/3+2^2/3=x-2.........from the first step

therefore R.H.S=2+4+6(x-2)=6+6x-12

hence x^3-6x^2+6x=6+6x-12

finally x^3-6x^2+6x-2=0

Therefore answer is 0

Akash Shukla
Jun 14, 2016

x = 2 + 2 1 3 + 2 2 3 x = 2+2^\dfrac{1}{3}+2^\dfrac{2}{3} ,

x = 2 1 3 ( 1 + 2 2 3 + 2 1 3 ) x= 2^\dfrac{1}{3}(1+2^\dfrac{2}{3}+2^\dfrac{1}{3})

x = 2 1 3 ( 2 + 2 2 3 + 2 1 3 1 ) x=2^\dfrac{1}{3}(2+2^\dfrac{2}{3}+2^\dfrac{1}{3}-1)

x = 2 1 1 3 ( x 1 ) x=2^1\dfrac{1}{3}(x-1)

cubing on both the sides

x 3 = 2 ( x 3 3 x 2 + 3 x 1 ) x^3 = 2(x^3-3x^2+3x-1)

x 3 6 x 2 + 6 x 2 = 0 x^3-6x^2+6x-2 = 0

0 pending reports

×

Problem Loading...

Note Loading...

Set Loading...