Stretching or compressing a spring increases its elastic potential energy. Within the limit of proportionality, Eₑ = ½ke² where e is extension in metres. Doubling extension at fixed spring constant makes the stored energy four times larger. Example: Extension triples for the same spring within its proportional range. Predict the stored energy change. Energy is proportional to extension squared, so it becomes 3² = 9 times larger. Use clear labels. Check your reasoning. Distinguish the quantities.