I'm not allowed to use trig substitutions to solve this, but I can use any other method. It's the integral of x/sqrt[16-x^2], I was plugging in 16-x^2 as u and -2x as du, so then it becomes -1/2 the integral of 1/sqrt[u] which simplifies to be -1/2sqrt[16-x^2] but I know from using the trig substitution method that the correct answer is actually only -sqrt[16-x^2], so where am I going wrong?