Question

X² - 4x +40=0 How do I solve this

Answer 1

Answer:

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.