During a flu epideic last year, a public health offical determined that the number of students infected by the flu virus was aprroximated by the function f(t)= (t-23)^2 + 625, where "t" is the number of days after the infection.
This year there is a new flu virus that can be aprroximated by f(t) = (t-25)^2 + 625. What kind of transformation describes the change between this year and last year?