the derivative of a function at the point exists if and only if the limit

exists

just show this limit does not exists if

use the same formula above, but now, can be anything but zero. just leave it as and find the answerif a (can not = 0), find g'(a)

or simply use the power rule to differentiate and plug in

hint: we have a vertical tangent line if the slope is infinite.show that y = x^(2/3) has a vertical tangent line at (0,0)

how does the derivative relate to the slope?