Evaluate. No Need for Calculators

Algebra Level 2

Evaluate: 3 5 2 11 2018 × 89 + 12 55 4036 \large \sqrt[2018]{3\sqrt{5} - 2\sqrt{11}} \times \sqrt[4036]{89+12\sqrt{55}}


The answer is 1.

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2 solutions

Hana Wehbi
Mar 6, 2018

To solve 3 5 2 11 2018 × 89 + 12 55 4036 \sqrt[2018]{3\sqrt{5} - 2\sqrt{11}} \times \sqrt[4036]{89+12\sqrt{55}}

Note that ( 3 5 + 2 11 ) 2 = 89 + 12 55 (3\sqrt{5}+2\sqrt{11})^2=89+12\sqrt{55}

then 3 5 2 11 2018 × 89 + 12 55 4036 = 3 5 2 11 2018 × ( 3 5 + 2 11 ) 2 4036 \sqrt[2018]{3\sqrt{5} - 2\sqrt{11}} \times \sqrt[4036]{89+12\sqrt{55}} = \sqrt[2018]{3\sqrt{5} - 2\sqrt{11}} \times \sqrt[4036]{(3\sqrt{5}+2\sqrt{11})^2}

( 3 5 2 11 ) 2018 × ( 3 5 + 2 11 ) 2018 = ( 3 2 × 5 ) ( 2 2 × 11 ) 2018 = 45 44 2018 = 1 \sqrt[2018]{(3\sqrt{5} - 2\sqrt{11})} \times \sqrt[2018]{(3\sqrt{5}+2\sqrt{11})}= \sqrt[2018]{(3^2\times 5) - (2^2\times 11)} = \sqrt[2018]{45-44} = \boxed{1}

Chew-Seong Cheong
Mar 29, 2018

3 5 2 11 2018 × 89 + 12 55 4036 = ( 3 5 2 11 ) 2 4036 × 89 + 12 55 4036 = ( 45 12 55 + 44 ) ( 89 + 12 55 ) 4036 = ( 89 12 55 ) ( 89 + 12 55 ) 4036 = 8 9 2 1 2 2 × 55 4036 = 7921 7920 4036 = 1 \begin{aligned} \sqrt[2018]{3\sqrt 5-2\sqrt{11}} \times \sqrt[4036]{89+12\sqrt{55}} & = \sqrt[4036]{\left(3\sqrt 5-2\sqrt{11}\right)^2} \times \sqrt[4036]{89+12\sqrt{55}} \\ & = \sqrt[4036]{\left(45-12\sqrt{55} + 44\right) \left(89+12\sqrt{55}\right)} \\ & = \sqrt[4036]{\left(89-12\sqrt{55}\right) \left(89+12\sqrt{55}\right)} \\ & = \sqrt[4036]{89^2-12^2\times 55} \\ & = \sqrt[4036]{7921-7920} \\ & = \boxed{1} \end{aligned}

Nice solution! But 89 ² = 7921 89²=7921 , not 7901 7901 , and 144 55 = 7920 144*55=7920 , not 7900 7900 .

Ong Zi Qian - 3 years, 2 months ago

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Thanks. A typo

Chew-Seong Cheong - 3 years, 2 months ago

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