Seeking monotonicity of function Judge the monotonicity of function f (x) = x + 4 / X (x > 0) Please write down the process, and are given

Seeking monotonicity of function Judge the monotonicity of function f (x) = x + 4 / X (x > 0) Please write down the process, and are given

Haven't you studied derivative in grade one of senior high school? It can only be proved by definition
analysis:
Let X1 > x2 > 0
f(x1)-f(x2)=(x1-x2)+4(1/x1-1/x2)
=(x1-x2)-4(x1-x2)/x1x
=(x1-x2)(1-4/x1x2)
If you want to judge the increase or decrease, you need to know the positive and negative of F (x1) - f (x2), and if (x1-x2) is positive, you need to judge the positive and negative of (1-4 / x1x2)
1 - / x1x2 = 0, that is, 1-1 / (the square of x) = 0, we can get x = 2, that is to say, we should take 2 as the dividing point
solution
1. When 0