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You've not applied the quotient rule correctly. You dropped a factor in the second term, and a 2.35 has been reduced to 2. it would help if you included all appropriate parentheses. Why have you substituted r = 9 in some places but not in others?

 

What you have written is (I think - you appear to have substituted R=9 in some places but not others):[tex]2.35(R+0.5)^2-\frac{2(R+0.5)}{(R+0.5)^4}[/tex]which I don't think is right. Even assuming that you meant [tex]\frac{2.35(R+0.5)^2-2(R+0.5)}{(R+0.5)^4}[/tex]I still don't think this is right. I was taught that the quotient rule as[tex]d\frac{u}{v}=\frac{vdu-udv}{v^2}[/tex]Perhaps you could show us what you think [itex]u, v, du, dv[/itex] are?