The previous contents and examples have explained the determination method of integral order and integral limit. Here, after integrating x and y, the range of y is determined. Take a little Y on the table and make it a parallel to the X axis. From left to right, it first intersects with parabola and then intersects with straight line, so the value range of x is y 2 to y+2.

Someone summed up the formula: first set a limit for the posterior product, draw a line within the limit, take the lower limit first, and then see the upper limit.