SOLUTION: for all real numbers x>0, we have x^2<= x^3

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Question 1125739: for all real numbers x>0, we have x^2<= x^3
Found 2 solutions by ikleyn, Theo:
Answer by ikleyn(52830)   (Show Source): You can put this solution on YOUR website!
.
This statement is not true.


Counter-example is x= , for example.


Answer by Theo(13342)   (Show Source): You can put this solution on YOUR website!
your inequality is x^2 <= x^3

subtract x^2 from both sides of this equation to get:

0 <= x^3 - x^2.

find the 0 points of the graph by setting x^2 - x^2 = 0

factor out an x^2 to get x^2 * (x-1) = 0

solve for x to get x = 0 or x = 1.

those are the 0 points of the graph (y = 0).

now you want to look at the intervals where x < 0 and x > 1 and 0 < x < 1.

since we only care about the intervals where x >= 0, then the intervals we are interested in are 0 < x < 1 and x > 1.

since the graph is continuous, if it is above the x-axis, it will stay above until it crosses a 0 point and if it is below the x-axis, it will stay below until it crosses a 0 point.

pick a value in each interval to test.

when x = .5, x^2 = .25 and x^3 = .125, therefore x^2 greater than x^3.

when x = 2, x^2 = 4 and x^3 = 8, therefore x^2 less than x^3.

the solution is that x^2 <= x^3 in the interval of x >= 1.

the following graph confirms that.

$$$


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