(√6+2√7)^2

20

(√6 + 2√7)^2 = (√6)^2 + 2 * √6 * 2√7 + (2√7)^2 = 6 + 2 * 2 * √6 * √7 + 4 * 7 = 6 + 4 * √(6 * 7) + 28 = 6 + 4 * √(6 * 7) + 28 = 4 * √42 + 34 = 4 * √42 + 34 = 34 + 4√42

Ответ: 34 + 4√42.