Verified answer

1

x^3 - 13x = 0

x(x^2 - 13) = 0

x(x - √13)(x + √13) = 0

x=0

x=-√13

x=√13

ответ x={-√13  √13  0}

используем a^2 - b^2 = (a - b)(a + b)

2

x^4 - 7x^2 + 12 = 0

x^2 = t >=0

t^2 - 7t + 12 =0

D= 49 - 4*12 = 1

t12=(7 +-1)/2 = 3   4

t=3

x^2 = 3

x=√3

x=-√3

t = 4

x^2 = 4

x=2

x=-2

ответ х={-2 2 -√3 √3}