How to solve using quadratic formula

Question

7x^2+140=0

x^2-4x=-10

Answer 1

You don't need the quadratic formula for first of these...but here it is

first one: divide by 7 first: x² + 20: [0±sqrt(0-80)]/2=2i80√5 as expected.

2nd one: [4±sqrt(16-80)]/2=2±4i

Answer 2

In standard form,

ax² + bx + c = 0

7x² + 140 = 0

a = 7

b = 0

c = 140

x = [-b ± √(b² - 4ac)] / (2a)

Plug in the numbers. For

x² - 4x = -10,

first put the equation in standard form.

x² - 4x + 10 = 0

a = 1

b = -4

c = 10

Plug in the numbers as in the example above.