5 − 4 x + 7 12 5 x 125 x 5 −4x+7 ​ start fraction, 5, start superscript, minus, 4, x, plus, 7, end superscript, divided by, 125, start superscript, x, end superscript, end fraction as 5 f ( x ) 5 f(x) 5, start superscript, f, left parenthesis, x, right parenthesis, end superscript ?