Find from first principles the differential coefficient of y with respect y=x

Answer 1

So find dy/dx when y = x ??

dy/dx = lim (h>0) [f(x+h) - f(x)]/h

when y=x, f(x) = x

dy/dx = lim (h>0) [ x+h - x] / h = lim (h>0) h/h = lim (h>0) 1 = 1

so when y=x, dy/dx = 1.