An irrational number is a number that cannot be expressed as a fraction of two integers, meaning it has a non-repeating and non-terminating decimal expansion.
Let's examine the options provided:
- -1 is a rational number because it can be written as -1/1.
- 5/29 is a rational number because it is a fraction of two integers.
- 0.343434 is a rational number because it has a repeating decimal (0.34 repeating can be expressed as a fraction).
- 87.98217 is a rational number because it has a finite decimal expansion and can be expressed as a fraction.
Since all the provided options are rational numbers, none of them is irrational. Therefore, the answer is:
None of the above options is an irrational number.