Ivy and Andrey were asked to find an explicit formula for the sequence -100,-50,0,50,...−100,−50,0,50,...m inus, 100, comma, minus, 50, comma, 0, comma, 50, comma, point, point, point, where the first term should be f(1)f(1)f, left parenthesis, 1, right parenthesis. Ivy said the formula is f(n)=-100+50(n-1)f(n)=−100+50(n−1)f , left parenthesis, n, right parenthesis, equals, minus, 100, plus, 50, left parenthesis, n, minus, 1, right parenthesis.
Andrey said the formula is f(n)=-150+50nf(n)=−150+50nf, left parenthesis, n, right parenthesis, equals, minus, 150, plus, 50, n.
Which one of them is right?