1. (a^3)^5 * a^-12 = a^15 * a^-12 = a^3 = 0.2^3 = 0.008
2. корень(2)*корень(50) + 3*корень(49) = корень(100) + 3 * 7 = 10 + 21 = 121
3. x^2 - 7x + 6 = 0
a = 1, b = -7, c = 6
D = b^2 - 4ac = 49 - 4*1*6 = 49 - 24 = 25 = 5^2
x1 = (7 + 5)/2 = 6
x2 = (7-5)/2 = 1