Bî-hun

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y = f(x) tī (x, f(x)) ê chhiat-soàⁿ ê chhiâ-lu̍t tō sī i tī x ê bî-hun.

sò͘-ha̍k, bî-hun sī 1 ê hâm-sò͘ chek-sî ê piàn-hoà-lu̍t. Bî-hun ham chek-hunbî-chek-hun 2 ê tiong-sim khài-liām, in 2 ê thaù-koè bî-chek-hun ki-pún tēng-lí koan-liân chò-hoé.