Because the solution set of this inequality is (-1/2, 1/3). So ax? The two solutions of equation +bx+2=0 are-1/2 and 1/3.

Then we can use the relationship between root and coefficient, x1+x2 =-b/ax1* x2 = c/a (c is 2. A=- 12 can be directly solved by this equation, and then b=-2 can be obtained by substituting it into the formula of 1.

2. Should be 1/2.

Because x, y ∈ r+, 2x+y=2. According to the basic inequality. It can be found that 2xy is less than or equal to 2 under the root number of 2 times, so 2xy under the root number is less than or equal to 1.

So xy is less than or equal to 1/2. So the maximum value of c is 1/2.

3. It should be {x ▏ x 3}

F(x) is monotonically increasing in (-∞, 0) because it is odd function and it is a decreasing function in (0, +∞).

Because x f (x) < 0 is required.

So x and f(x) must have different signs.

The answer is {x ▏ x 3}