Firstly,

I keep getting a LaTex Error with the following equation:

y=\int(x+\frac{20}{x^2}+\frac{5}{x^2})dx

Secondly, my teacher said the answer to the following question is c=3.9, but I keep getting a different answer:

Here is my working:Integrate the following equation to find the particular solution

y= integral of (x + 20/x^3 + 5/x^2)dx, where x = 3 and y = 9

y = [(x^2)/2] + [(20x^-2)/-2] + [(5x^-1)/-1] + C

y = [(x^2)/2] - (10x^-2) - (5x^-1) + C

y = [(x^2)/2] - (10/x^2) - (5/x) + C

9 = [(3^3)/2] - (10/3^2) - 5/3 + C

9 = 4.5 - 1.1 - 1.6 + C

9 - 4.5 + 1.1 + 1.6 = c

C = 7.2 (My teacher's answer is C=3.9)

What did I do wrong with LaTex, and this answer?