79. which of the following are functions? (1) [(x, y): y2 = x, x, y e r]| (2) ((x, y): y = |x|, x, y er] (3) ( x, y):x2 + y2 = 1, x, y e r]| (4) i( x, y):x2 -y?

79. Which of the following are functions? (1) [(X, Y): Y2 = X, X, Y e R]| (2) ((X, Y): Y = |X|, X, Y eR] (3) ( X, Y):X2 + y2 = 1, X, Y e R]| (4) I( X, Y):x2 -y? = 1, X, Y e R] 80. The domain of definition of f (X) = V4X - x2 is 9RTTA f(X) = v4x - x? m st T (1) R-[0, 41 (2) R-(0, 4) (3) (0,4) (4) [0,4] 81. Differential of x with respect to X will be (1) x2.log X (2) x2-log X (3) Xl + log X) (4) X (1+ log X) 82. Diffcrential of X with respect to X will be (1) xlog X,1 (2) x1ogx 3) Rlog X 2X X