Look at this sequence of numbers: 0, 1, 2, 4, 6, 9, 12, 16, ? - what number should replace the question mark?

20

Step-by-step explanation:

0 to 1 = a difference of 1

1 to 2 = a difference of 2-1 = 1

2 to 4 = a difference of 2

4 to 6 = a difference of 2

6 to 9 = a difference of 3

9 to 12 = a difference of 3

12 to 16 = a difference of 4

16 to 20 = a difference of 4

{x = -1/2 ,   y = -1

step-by-step explanation:

solve the following system:

{2 x + y = -2

{10 x - 3 y = -2

in the first equation, look to solve for y:

{2 x + y = -2

{10 x - 3 y = -2

subtract 2 x from both sides:

{y = -2 x - 2

{10 x - 3 y = -2

substitute y = -2 x - 2 into the second equation:

{y = -2 x - 2

{10 x - 3 (-2 x - 2) = -2

10 x - 3 (-2 x - 2) = (6 x + 6) + 10 x = 16 x + 6:

{y = -2 x - 2

{16 x + 6 = -2

in the second equation, look to solve for x:

{y = -2 x - 2

{16 x + 6 = -2

subtract 6 from both sides:

{y = -2 x - 2

{16 x = -8

divide both sides by 16:

{y = -2 x - 2

{x = -1/2

substitute x = -1/2 into the first equation:

{y = -1

{x = -1/2

collect results in alphabetical order:

answer:   {x = -1/2 ,   y = -1

68719476736

step-by-step explanation:

8*8*8*8*8*8*8*8*8*8*8*8=68719476736