The Cube Is Good, But The Square Is Not

Algebra Level 1

Is there a number which is equal to its cube but not equal to its square?

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6 solutions

Tunk-Fey Ariawan
Mar 18, 2014

Let x x be the number, x 3 = x x^3=x and x 2 x x^2\neq x . x 3 = x x 3 x = 0 x ( x 2 1 ) = 0 x ( x 1 ) ( x + 1 ) = 0 x 1 = 0 , x 2 = 1 , and x 3 = 1. \begin{aligned} x^3&=x\\ x^3-x&=0\\ x(x^2-1)&=0\\ x(x-1)(x+1)&=0\\ x_1=0,\; x_2=1,&\text{and}\;x_3=-1. \end{aligned} Therefore, only x 3 = 1 x_3=-1 that meets the condition because ( 1 ) 3 = 1 (-1)^3=-1 and ( 1 ) 2 1 (-1)^2\neq -1 .

It has been proven without any reasonable doubt.

Kavya Bagga
Mar 21, 2016

-i^3 is also one number. cube of -i^3 is also -i^3 but it's square is -1

Actually, although the square of (-i) is (-1), its cube is (+i)

Alija Bevrnja - 5 years, 2 months ago

Please explain properly do not make fool other

gurpreet maini - 4 years, 11 months ago

Kavya bagga

gurpreet maini - 4 years, 11 months ago

(-1)^3=-1 Equal (-1)^2=1 Not Equal

Kapil Mittal
Apr 28, 2014

(-1)^3 = -1 but (-1)^2 = 1

Bill Bell
Aug 1, 2014

i is also a number, and it would appear to be a solution.

@Bill Bell No, i 3 = i i i^3=-i\neq i and i 2 = 1 i i^2=-1\neq i . i i is neither equal to its cube nor to its square.

Abdur Rehman Zahid - 5 years, 3 months ago

Log in to reply

Oh, dear, you're right.

Bill Bell - 5 years, 3 months ago
Jasveen Sandral
Mar 18, 2014

x3 = x

x2 x

x3 - x = 0

x(x2 - 1) = 0

x(x + 1)(x - 1) = 0

x = 0 or 1 or -1

02 = 0

12 = 1

Thus, answer is -1

Hey it's not level 2 question it's level 1 plz modify it

Adarsh Mahor - 5 years, 2 months ago

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