Answer:
a15 = 58x + 63
Step-by-step explanation:
number of terms (n) = 15
first term (a1) = 2x + 7
second term (a2) = 6x + 11
common difference (d) = a2-a1 = 6x + 11 - (2x + 7)
= 6x + 11 - 2x - 7
= 4x + 4
= 4(x + 1)
15th term (a15) = ?
equation :
a15 = a1 + (n - 1) × d
a15 = 2x + 7 + (15 - 1) × 4(x + 1)
a15 = 2x + 7 + 14 × 4 × (x + 1)
a15 = 2x + 7 + 56(x + 1)
a15 = 2x + 7 + 56x + 56
a15 = 58x + 63
