Multiply Me

Algebra Level 1

I have a number.

If I multiply it by itself, then it will become larger than before.

If I multiply this new number by the original number one more time, then it will become smaller than ever before.

If I multiply this latest number by the original number yet again, then it will become __________ . \text{\_\_\_\_\_\_\_\_\_\_}.

smaller than all the previous 3 numbers the same original number that I started with larger than all the previous 3 numbers

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2 solutions

Tapas Mazumdar
Oct 18, 2016

Let my number be x x .

Let's check the given statements one by one.

If I multiply it by itself, then it will become larger than before.

Here,

x 2 > x x 2 x > 0 x ( , 0 ) ( 1 , ) x^2 > x \\ \implies x^2 - x > 0 \\ \implies x \in (-\infty, 0) \cup (1, \infty)

If I multiply this new number by the original number one more time, then it will become smaller than ever before.

Here,

x 3 < x x 3 x < 0 x ( x + 1 ) ( x 1 ) < 0 x ( , 1 ) ( 0 , 1 ) x^3 < x \\ \implies x^3 - x < 0 \\ \implies x(x+1)(x-1) < 0 \\ \implies x \in (-\infty,-1) \cup (0,1)

From the set of two obtained ranges of x x , we conclude that,

x ( , 1 ) x \in (-\infty,-1)

Thus, x x is a negative real number less than 1 -1 .

Since the even power of a negative real number is always positive and x > 1 |x|>1 , therefore when I multiply my number by itself four times I will obtain the number x 4 x^4 which will be positive as well as it will be greater than all of x , x 2 x, \ x^2 and x 3 x^3 .

Y H
Oct 20, 2016

The number is neither 0 nor 1, neither of which is greater when it is squared (#1). Nor is it greater than 1, because then cubing it would result in a greater number (#2). Nor is it between negative one and zero, because cubing it would also result in a greater number (#2). Nor is it -1, because cubing it works result in a number equal to the original (#2). Therefore it is a number less than -1 in order to fulfill there three conditions. Raising such a number to the fourth power results in as negative number less than all the others

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