f(x)=-2x+3
Let x1> x2
f(x 1)-f(x2)
=-2x 1+3-(-2x2+3)
=-2x 1+2x2
= 2(x2-x 1)& lt; 0
Therefore: f (x 1)
So: f(x)=-2x+3 is a decreasing function on R.
10. Solution:
F(x) is the decreasing function of r, f(x? +2)& lt; Female (3x)
So: x? +2 & gt; 3x
So: x? -3x+2 >0
So: (x- 1)(x-2)>0.
So: x < 1 or x>2.