Answer to Question #989 in Algebra for gabriel

Question

how do you figure out a a formula for a sequence than whats the ninth term, Ex 2 4 6 8

Answer 1

It's the aruthmetic progression, a[n] = a₁ +(n-1)*b, where b = 2, a₁ = 2;
so
a[9] = 2 + (9-1)*2 = 18.