Which group of number are all perfect squares

a: 1,16,27,
b: 4,39,64
c: 9,49,81,
d: 10,25,35

What is the inverse of the function f(x) = 2x + 1?

[10 points, algebra 2]according to my answer key the restrictions are -1 and 4. but why not positive 1?

Cody was 165cm tall on the first day of school this year, which was 10% taller than he was on the first day of school last year.