-x^2+4x-13 = 0
x^2 - 4x + 13 = 0 Use quadratic formula
\(x = {-b \pm \sqrt{b^2-4ac} \over 2a}\) a = 1 b = -4 c = 13
Sustituting yields 4 +- sqrt( 16- 4*1*13) / 2 = 2 +-sqrt (-36)/2 = 2 +- 3i
Think you can try the others?
b ) x^2 + 41 = -8x
x^2 + 8x = -41 complete the square on x
x^2 + 8x + 16 = -41 + 16
(x + 4)^2 = - 25 take both roots
x + 4 = ±√-25
x + 4 = ± 5i subtract 4 from both sides
x = - 4 ± 5i