Question

Write the 8th term of each pattern.
a. 15, 24, 42, 78, 150

Answer 1

$a_1=15\\a_2=2a_1-6=2\cdot15-6=30-6=24\\a_3=2a_2-6=2\cdot24-6=48-6=42\\a_4=2a_3-6=2\cdot42-6=84-6=78\\a_5=2a_4-6=2\cdot78-6=156-6=150\\a_6=2a_5-6=2\cdot150-6=300-6=294\\a_7=2a_6-6=2\cdot294-6=588-6=582\\a_8=2a_7-6=2\cdot582-6=1164-6=1158\\\\ \left\{\begin{array}{ccc}a_1=15\\a_n=2a_{n-1}-6\end{array}\right$