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
Answer:
I think 5 and 7 I got that question
Term: 3 4 5
Value 20 .. 5
20 20r 20r^2
So 20r^2 = 5
r^2 = 1/4
r = 1/2
