佢prove existence 果度,點解S唔洗細過b? 跟住佢put k=2a證S exists。。。a-2ab仲點會細過ba-2ab 點解要細過b?個argument係 1-2b < 0 then a*(1-2b) > 0 then a - b*2a > 0 so a - b*2a ∈ S 同埋唔係證S exist,係證S non empty
佢prove existence 果度,點解S唔洗細過b? 跟住佢put k=2a證S exists。。。a-2ab仲點會細過b