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Grade 12thAlgebra

Find all the integral solutions of x(cube) = 6y(cube) + 20z(cube)

Profile image of Abhishek Patil
14 Years agoGrade 12th
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3 Answers

Profile image of Rahul Kumar
14 Years ago

Since there are three variables x,y,z.Hence we need three equations to solve them

Profile image of Abhishek Patil
14 Years ago

I have asked for integral solutions not its exact value. If it was to be exact value then three equations were required but I need integral solutions.

Profile image of mycroft holmes
14 Years ago

Its evident that x is even. This means LHS is divisible by 8

 

Now if y is odd and z even, then RHS leaves remainder 6 on division by 8

 

If y is even and z is odd, then RHS leaves remainder 4

 

If both y and z are odd, then RHS leaves remainder 2.

 

Hence y and z are both even

 

Let x=2p, y=2q, z=2r. Then after cancellation we have 

 

That means if (x,y,z) is a solution so is (p,q,r).

 

But this process can be continued indefinitely, which is absurd (Infinite Descent)

Hence no solutions are possible