Pattern: 0, 1, 3, 6, 10, 15, __
explain the pattern of these numbers.

21

Step-by-step explanation:

0 + 1 = 1

1 + 2 = 3

3 + 3 = 6

6 + 4 = 10

10 + 5 = 15

15 + 6 = 21

Each number is added to an increase of 1 - first add 1, then add 2, then add 3,etc

Not listed but next would be 21 + 7 = 28  

so it would be 0, 1, 3, 6, 10, 15, 21, 28

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

16 is the absolute value

step-by-step explanation: