The geometric mean is different than algebraic mean - algebraic is adding up all the numbers and dividing it by the number of numbers, but geometric is multiplying them and getting the root of the product of all the numbers. For example, if there were 10 numbers, we would have the 10th root of the product of all the numbers or the product to the power of 1/10.
Since there are 2 numbers, we simply have the square root -
due to that 2²=4, so we can divide what is in the square root by that and take the 2 out.
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