The phrase "and cannot be solved" is correct and usable in written English.
It can be used to describe a problem or situation that has no solution or resolution.
Example: "The equation presented in the paper is complex and cannot be solved using traditional methods."
Alternatives: "and remains unsolvable" or "and has no solution".
"California's electricity problems developed over a period of years and cannot be solved overnight.
The crisis is elsewhere and cannot be solved by single governments.
The tasks are very serious and cannot be solved in two or three months.
Most if not all of these problems stem from a broken corporate culture and poor management, and cannot be solved by simply adding funding and also personnel.
Climate change has been caused by ignorance and stupidity and cannot be solved by endorsing more of the same with geo-engineering.
If so, around one-third of the rise in America's joblessness is impervious to the business cycle and cannot be solved by boosting demand (see article).
Experts inside and outside government see the project as an opportunity to win the peace, though Kurdish grievances extend beyond poverty to issues of ethnic identity and equality, and those cannot be solved by providing electricity and jobs.
"Developed countries," he said, "tend to see an unforgiving problem with potentially grave and irreversible consequences and that cannot be solved without the full participation of developing countries, particularly China and the other emerging market economies".
However, numerous challenges in engineering include continuous and discrete phase simultaneously, and therefore cannot be solved only by continuous or discrete approaches.
This leads the solution to be nonconvex because the Lyapunov function and the controller matrix are coupled and therefore cannot be solved by semidefinite programming (SDP).
"Racism and homophobia cannot be solved by longer prison sentences".
