X² - 4x + 40=0

How do I solve this

x = 2 + 6i, x - 6i.

Step-by-step explanation:

To factor this you need 2 numbers whose product is + 40 and whose sum is - 4. There are no such numbers so we could use the method of completing the square:

x^2 - 4x + 40 = 90

x^2 - 4x = - 40

(x - 2) ^2 - 4 = - 40

(x - 2) ^2 = - 36 - So the roots are complex numbers:

x - 2 = + / -√36

x = 2 + 6i, x - 6i.