How to Solve using quadratic formula

Question

7x²+140=0

My answer X=+-2isqrt5

x²-4x=-10

My answer X=2+-isqrt6

Answer 1

7x² + 140 = 0

This one does not need the quadratic formula.

rearrange and simplify:

x² = -20

x = ±√-20 = ±2 * i√5

x² - 4x = -10

I'll check by completing the square:

x² - 4x + 4 = -10 + 4

(x - 2)² = -6

x - 2 = 2 ± i√6

You got them both right!!