Answer:
x = -28
Explanation:
x4 + 13x2 + 42 = 0
Reorder the terms:
42 + 13x2 + x4 = 0
Solving
42 + 13x2 + x4 = 0
Solving for variable 'x'.
Factor a trinomial.
(7 + x2)(6 + x2) = 0
Simplifying
7 + x2 = 0
Solving
7 + x2 = 0
Add '-7' to each side of the equation.
7 + -7 + x2 = 0 + -7
Combine like terms: 7 + -7 = 0
0 + x2 = 0 + -7
x2 = 0 + -7
Combine like terms: 0 + -7 = -7
x2 = -7
Simplifying
x2 = -7 = -28