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Algebra Difficulty 2.1 Junior Find the answer

The value of x2\frac{x}{2} is less than the value of x2x^{2}. The value of x2x^{2} is less than the value of xx. Which of the following could be a value of xx?

A number or a short expression. Spacing and $ signs are ignored.

Solution

Since x2<xx^{2}<x and x20x^{2} \geq 0, then x>0x>0 and so it cannot be the case that xx is negative. Thus, neither (D) nor (E) is the answer. Since x2<xx^{2}<x, then we cannot have x>1x>1. This is because when x>1x>1, we have x2>xx^{2}>x. Thus, (A) is not the answer and so the answer is (B) or (C). If x=13x=\frac{1}{3}, then x2=13×13=19x^{2}=\frac{1}{3} \times \frac{1}{3}=\frac{1}{9} and x2=1/32=16\frac{x}{2}=\frac{1 / 3}{2}=\frac{1}{6}. Since 16>19\frac{1}{6}>\frac{1}{9}, then (B)(B) cannot be the answer. Therefore, the answer must be (C). Checking, when x=34x=\frac{3}{4}, we have x2=916x^{2}=\frac{9}{16} and x2=38\frac{x}{2}=\frac{3}{8}. Since x2=38=616<916=x2\frac{x}{2}=\frac{3}{8}=\frac{6}{16}<\frac{9}{16}=x^{2}, then x2<x2\frac{x}{2}<x^{2}. Also, x2=916<1216=34=xx^{2}=\frac{9}{16}<\frac{12}{16}=\frac{3}{4}=x. This confirms that x=34x=\frac{3}{4} does satisfy the required conditions.

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