What is the pattern of 1,3,6,10,15 and the next number in the pattern?

The next number is 21

3 = 1 + 2
6 = 3 + 3
10 = 6 + 4
15 = 10 + 5
21 = 15 + 6

y = 3x+4

step-by-step explanation:

to find the slope

slope = (y2-y1)/ (x2-x1)

    = (-8-4)/ (-4-0)

    = -12/-4

  = 3

using the slope intercept form of a line

y= mx+b

we know the slope is 3

we know the y intercept is 4 ( the point where it crosses the y axis or x=0)

y = 3x+4