∵? ∴? ∽? ∠? Δ? √? x⊥''
By f(x)=x-2x,
Get an f? (x)=2x-2
By f? (x)=2x-2=0
X= 1。
In (-∞, 1), f? (x)& lt; 0, and the decreasing interval is (-∞,1);
In (1, +∞), f? (x)>0, and the increment interval is (1, +∞).
therefore
F(x)=x-2x, and the decreasing interval of f is (-∞,1); The increment interval is (1, +∞).
Method 2: (mirror image method)
As shown in the figure.
To observe the image, you must
F(x)=x-2x, and the decreasing interval of f is (-∞,1); The increment interval is (1, +∞). ?