Using differentials find dy and delta y when y=7/x and dx=delta x =1
Perhaps you mean x = delta x = 1 ???
y = 7 x^-1
dy/dx = 7 (-1)x^-2 = -7 x^-2
if x = 1
y = 7/1 = 7
dy/dx = -7
delta y = -7 delta x
if delta x = 1
delta y = -7
Y + delta Y = 7-7 = 0
real answer
y (2) = 7/2 = 3.5