Which of the following are monotonic transformations? 

(1) u = 2v − 13; 

(2) u = −1/v²; 

(3) u = 1/v²;  

(4) u = lnv;  

(5) u = −e^−v; 

(6) u = v²; 

(7) u = v² for v > 0;

(8) u = v² for v < 0.