Explicit formulas for arithmetic sequences

Carlos and Ana were asked to find an explicit formula for the sequence $-10,-4,2,8,...$minus, 10, comma, minus, 4, comma, 2, comma, 8, comma, point, point, point, where the first term should be $f(1)$f, left parenthesis, 1, right parenthesis.

Carlos said the formula is $f(n)=-10+6n$f, left parenthesis, n, right parenthesis, equals, minus, 10, plus, 6, n.

Ana said the formula is $f(n)=-10+6(n-1)$f, left parenthesis, n, right parenthesis, equals, minus, 10, plus, 6, left parenthesis, n, minus, 1, right parenthesis.