(3√10 - √5)² = (3√10)² - 2 · 3√10 · √5 + (√5)² = 9·10 - 6√50 + 5 = 95 - 6·5√2 =
= 95 - 30√2.
√(√7 + 4) · √(4 - √7) = √((√7 + 4)·(4 - √7)) = √(4² - (√7)²) = √(16 - 7) = √9 = 3.
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(3√10 - √5)² = (3√10)² - 2 · 3√10 · √5 + (√5)² = 9·10 - 6√50 + 5 = 95 - 6·5√2 =
= 95 - 30√2.
√(√7 + 4) · √(4 - √7) = √((√7 + 4)·(4 - √7)) = √(4² - (√7)²) = √(16 - 7) = √9 = 3.