If I can paint a wall in 20 min and my friend can paint a wall in 30 min. How many minutes would it take for us to paint a wall working together.

Step-by-step explanation:

Given

It takes 20 min and 30 min for  a person and his friend to paint a wall individually  i.e.

In 1 min they cover part and part of wall respectively.

If the work together, 1 minute work is

Time required will be reciprocal of it

10 down (bang1)

5 up

5down (2)

2.5 up

2.5 down (3)

1.25 up

1.25 down (4)

now add them up : )

hoped i lol

the first one is x^2+2x+2

the second one is x^2+4

the last one is x^2-4x+8