If the monotone decreasing intervals of the function f (x) = (x-a) / x2 are (- infinity, 0) and (2, + infinity), then the real number a=________ .

If the monotone decreasing intervals of the function f (x) = (x-a) / x2 are (- infinity, 0) and (2, + infinity), then the real number a=________ .

f'(x)=[x²-(x-a)*2x]/x^4
=(x²-2x²+2ax)/x^4
=-(x²-2ax)/x^4
Let f '(x)

When the independent variable x______ The value of function y = 5x + 4 is greater than 0______ The value of y = 5x + 4 is less than 0

If the value of function y = 5x + 4 is greater than 0, then 5x + 4 ＞ 0, the solution is x ＞ - 45; if the value of function y = 5x + 4 is less than 0, then 5x + 4 ＜ 0, the solution is x ＜ - 45. That is, when the independent variable x ＞ - 45, the value of function y = 5x + 4 is greater than 0; when x ＜ - 45, the value of function y = 5x + 4 is less than 0

Given the function y = - 3 / 5x + 1 (1), when the function value y is a positive number, find the value range of the independent variable x

-3/5X+1>0
-3/5X>-1
x

When the independent variables of the following functions are in what range, the value of the function is greater than 0, less than 0 or equal to 0:
(1) The square of y = x-2x-10
(2) Y = - x squared - 2x + 3
(3) Y = the square of X + 7x-8
(4) Y = - x squared + 2x + 8

If a is not equal to 0, we can see that y = ax ^ 2 + BX + C is a parabola. When a > 0, the opening is upward. (1) if X1 and X2 do not exist, then y is always greater than 0. (2) if X1 and X2 exist and are the same, then y is 0 at X1 = X2, and all other places are greater than 0. (3) if X1 and X2 exist and do not