10. Infinitely many solutions:
Simplify this equation:
When the equation becomes
This equality is true for all x, thus the equation has infinitely many solutions.
11. The equation should have one solution x=-1.
First, simplify the equation:
This equation will have solution x=-1 when
Therefore, the initial equation is
12. The equation should have infinitely many solutions.
Simplify it:
When this equation will have infinitely many solutions.