Maths Olympiad Prep

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Algebra Difficulty 1.0 Junior Prove it Canada

What is the value of 32232332\dfrac{3^2-2^3}{2^{3}-3^{2}} ?
What is the value of 81+964\sqrt{\sqrt{81}+\sqrt{9}-\sqrt{64}} ?
Determine all real numbers xx for which $1x2\$\dfrac{1}{\sqrt{x^2}} + 7}} =
14$.\dfrac{1}{4}\$.

Solution

Evaluating, 3 2\text{3 2} - 2^3}{2^3 -
3^2} = 9\text{9} - 8}{8-9} = 11\dfrac{1}{-1} = -1$.

Alternatively, since $2^3 - 3^2 = -(3^2 -
2^3),then, then 3 2\text{3 2} - 2^3}{2^3 -
3^2} = -1$.
Evaluating, $(81+964=9\$\sqrt{\phantom{\left(\right.}\hspace{-2mm}\sqrt{81}+\sqrt{9}-\sqrt{64}} = \sqrt{9} + 3 - 8} = 4\sqrt{4} = 2$.
Since $1x2\$\dfrac{1}{\sqrt{x^2}} + 7}} =
14\dfrac{1}{4},then, then x2\sqrt{x^2} + 7} =
4$.

This means that x2+7=42=16x^2 + 7 = 4^2 = 16
and so x2=9x^2 = 9.

Since x2=9x^2 = 9, then x=±3x = \pm 3.

We can check by substitution that both of these values are
solutions.

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Source: CEMC, University of Waterloo, licensed CC-BY-NC-4.0. Statement reproduced verbatim; metadata (topic, difficulty) added by this project.