21)
= a₁ + d(n - 1) ; where a₁ is the first term and d is the difference.
a₁ = 3, d = 4 →
= 3 + 4(n - 1) = 3 + 4n - 4 = 4n - 1
= 4(25) - 1 = 100 - 1 = 99
=

=
=
= 51 · 25 = 1275
Answer:
= 4n - 1 , 1275
23)
= a₁ + d(n - 1) ; where a₁ is the first term and d is the difference.
a₁ = 4, d = 10 →
= 4 + 10(n - 1) = 4 + 10n - 10 = 10n - 6
= 10(25) - 6 = 250 - 6 = 244
=

=
=
= 124 · 25 = 3100
Answer:
= 10n - 6 , 3100