As you know, the area of a square is the square of the side length. It can be helpful here to make use of the form for the square of a binomial.
(a -b)² = a² - 2ab + b²
(√2 -3√5)² = (√2)² - 2(√2)(3√5) + (3√5)²
= 2 - 6√10 + 3²(5)
= 47 -6√10
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<em>Check</em>
√2-3√5 ≈ -5.29399 . . . . . . . . note that a negative value for side length makes no sense, so this isn't about geometry, it's about binomials and radicals
He is not making a valid inference because he is assuming the student populations interest based on a small part/ group of the student population, his class.
