3000√(x^2 +9) + 7000√(125 - 20x + x^2)

the answer i get is 3000x / √(x^2+9) + 7000(x - 10) / √(125 - 20x + x^2)

the answer that is given is 3000x / √(x^2+9) - 7000(10 - x) / √(125 - 20x + x^2)

My question is where does the minus sign come from?

3000√(x^2 +9) + 7000√(125 - 20x + x^2)

the answer i get is 3000x / √(x^2+9) + 7000(x - 10) / √(125 - 20x + x^2)

the answer that is given is 3000x / √(x^2+9) - 7000(10 - x) / √(125 - 20x + x^2)

My question is where does the minus sign come from?

Your answer and the given answer are equivalent because 7000(x-10) = 7000( -10+x) = -7000(10-x)

I think your answer is the slightly better one because there are fewer negative signs; aesthetically, that is preferred.