David can paint the living room in 4 hours and anna can paint it in 6 hours. how long will it take the two of them to paint the living room if they work together?

12/5 = 2.4

Step-by-step explanation:

In 4 hours, David can paint 1 room

In (4/4)=1 hour, David can paint 1/4 of the room

Similarly,

In 6 hours, Anna can paint 1 room

In 1 hour, Anna can paint 1/6 of the room

Therefore,

In one hour, they can paint (1/4 + 1/6) of the room if they work together

                                             = 5/12

So,

They can paint 1 room in 12/5 hours

                                         = 2.4 hours

x² + 3x + 7 = 0       [ax² + bx + c]

a = 1

b = 3

c = 7

quadratic formula:

    (+/- is this ±)

plug in the numbers into the variables

your answer is a