Definition

𝑦𝑘+1=𝑦𝑘+Δ𝑡𝑓(𝑡𝑘,𝑦𝑘)

when it’s linear, we can say

𝑦𝑘+1=𝑦𝑘+Δ𝑡𝜆𝑦𝑘=𝑦𝑘(1+Δ𝑡𝜆)

Stability

It’s stable only if all 𝜆: |1+𝜆𝑖|1