Help please!!! I don't understand this!! Can you please show me how to do this??

x*2+4=0 x*2=-4 x=do root of -4   can't possible to do root of -4

x² + 4 = 0      - 4  - 4        x² = -4        x = 2i x² - 6x + 7 = 0 x = -(-6) +/- √((-6)² - 4(1)(7))                      2(1) x = 6 +/- √(36 - 28)                  2 x = 6 +/- √(8)             2 x = 6 +/- 2√(2)              2 x = 3 + √(2) x = 3 + √(2)      x = 3 - √(2)