Given that \(81\times 2^{2n-2} = K, find \sqrt{K}\)

Assessment: WAEC SSCE - General Mathematics - 1999 (Objective) Subject: General Mathematics

Question 1 Report

Given that \(81\times 2^{2n-2} = K, find \sqrt{K}\)

Answer Details

To find K \sqrt{K} given that 81 × 2 2 n − 2 = K 81 \times 2^{2n-2} = K , we need to simplify the

expression step-by-step.

First,

rewrite 81 81 in terms of powers of 3 3 : 81 = 3 4 81 = 3^4

So,

the given equation becomes: K = 3 4 × 2 2 n − 2 K = 3^4 \times 2^{2n-2}

Next,

we need to find K \sqrt{K} : K = 3 4 × 2 2 n − 2 \sqrt{K} = \sqrt{3^4 \times 2^{2n-2}}


Using the property of square roots a × b = a × b \sqrt{a \times b} = \sqrt{a} \times \sqrt{b} : K = 3 4 × 2 2 n − 2 \sqrt{K} = \sqrt{3^4} \times \sqrt{2^{2n-2}}


Since 3 4 = 3 2 = 9 \sqrt{3^4} = 3^2 = 9 and 2 2 n − 2 = 2 ( 2 n − 2 ) / 2 = 2 n − 1 \sqrt{2^{2n-2}} = 2^{(2n-2)/2} = 2^{n-1} : K = 9 × 2 n − 1 \sqrt{K} = 9 \times 2^{n-1}


Thus, the correct answer is: 9 × 2 n − 1 \boxed{9 \times 2^{n-1}}  = 

9×2n−1

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