Answer:
(d) a1 = 11
Step-by-step explanation:
Put the numbers in the given formula and solve for a1.
a5 = 176 = a1(r^(5-1)) = a1·r^4
a7 = 704 = a1(r^(7-1)) = a1·r^6
Dividing a7 by a5 gives ...
a7/a5 = (a1·r^6)/(a1·r^4) = r^2 = 704/176 = 4
Then a1 is ...
a1 = a5/(r^4) = 176/(r²)² = 176/(4²) = 11
The first term is 11.
