Determine the 10th and 21st terms of the arithmetic sequence- 4+7x, 5+9x, 6+11x

Answer 1

5+9x - (4+7x) = 1+2x

a = 4+7x
d = 1+2x

T10 = a+9d = 4+7x + 9(1+2x) = 13+25x
T21 = a+20d = 4+7x + 20(1+2x) = 24+47x

Answer 2

T10 = 4 + 7x +(10-1)1+2x
= 4 + 7x +9(1+2x)
= 4 + 7x +9+18x
= 13+25x
T21 = 4+7x +(21-1)1+2x
= 4+7x +20(1+2x)
= 4+7x +20+40x
= 24+47x