Question

Find the derivative of f(x) = -9/x at x = 6

Answer 1

f(x)=-9/x which is equal to:

f(x)=-9x^(-1)  So the power rule for differentiation is used...

Power rule:  f(x)=x^e, df/dx=ex^(e-1) so:

df/dx=-9(-1)x^(-1-1)

df/dx=9x^(-2)  or if you prefer...

df/dx=9/x^2

df/dx(6)=9/36=1/4