Корень 15 + х + корень 3+х = 6

15 + x + 2√ (15 + x) (3 + x) + 3 + x = 36

2x + 18 + 2√ (x + 15) (x + 3) = 36

x + 9 + √ (x + 15) (x + 3) = 18

√ (x + 15) (x + 3) = - x + 9

(x + 15) (x + 3) = (-x + 9) ^2

x^2 + 18x + 45 = x^2 - 18x + 81

18x + 45 = - 18x + 81

18x + 18x = 81 - 45

36x = 36

x = 1