1 | initial version |

The solution `[[S == r7, I == 0, R == r8]]`

should be read as follows: the set of solutions is an infinite two-parameter space, which can be parametrized by two anonymous parameters `r7`

and `r8`

that Sage created for the purpose of describing the solution set. Each time you solve a new equation whose set of solutions is huge, Sage will create new symbolic variables to serve as a parameters to describe the solutions set.

2 | No.2 Revision |

The solution `[[S == r7, I == 0, R == r8]]`

should be read as follows: the set of solutions is an infinite two-parameter space, which can be parametrized by two anonymous parameters `r7`

and `r8`

that Sage created for the purpose of describing the solution set. Each time you solve a new equation whose set of solutions is huge, Sage will create new ~~symbolic variables ~~parameters (symbolic variables) to serve as a parameters to describe the solutions set.

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