Find p if the coefficient of x² in (1-2x)^p is 40

Picked one by one from a mixed channel; title passed two strict editor passes and the clickbait rules.

A 6-minute video from Tambuwal Maths Class: “Find p if the coefficient of x² in (1-2x)^p is 40”.

Video by Tambuwal Maths Class, played through YouTube's embedded player.