Solving the equation in the application problem (in line with the practical significance)

An equation with a domain (the answer should be in the range of x)

Quadratic radical equation (the number of roots and the roots are non-negative. Substitute x into the original equation and calculate again)

When discussing absolute value equations, the solution should be within the scope of discussion.

Generally, the calculation test only depends on whether the answer is correct, and the test need not be written on the test paper (the above items are very important)