Equation, which is elementary arithmetic. In the formula of elementary arithmetic, the calculation process is expressed by equations in turn according to the operation order, and such equations are called recursive equations.

For example:

485 - ( 6 × 4 + 32 )

= 485 - ( 24 + 32 )

= 485 - 56

= 429

In layman's terms, like this, there are many equal signs, and the neatly arranged equal signs are recursive equations.