The quantity of an element is decaying over time such that the amount of material at any time is given by the function R, left bracket, t, right bracket, equals, 900, left bracket, 0, point, 7, right bracket, start superscript, 2, t, plus, 1, end superscript, .R(t)=900(0.7) 2t 1 . Write an equivalent function of the form .R(t)=ab t .