Number pyramid problem (algebra 1)

Question

Write an equation that can be used to find d, the difference between the last number and the first number, for any row r. (Show work please)

Row 2; 8 10

Row 3; 15 17 19

Row 4; 24 26 28 30

Row 5; 35 37 39 41 43

Row 6; 48 50 52 54 56 58

Answer 1

the difference in the last and first number in row 2 is 2

so, 2 times 1

the difference in the last and first number in row 3 is 4

so, 2 times 2

the difference in the last and first number in row 4 is 6

so, 2 times 3

the difference in the last and first number in row n is 2 times n-1

so, d = 2(n-1) = 2n-2