二に元げん方ほう程てい式しき

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Meanings

1

noun

equation with two unknowns

mathematics

Mathematical term for an equation containing two unknown variables, typically x and y.

二two, two radical (no. 7)

元beginning, former time, origin

方direction, person, alternative

程extent, degree, law

式style, ceremony, rite

連れん立りつ方ほう程てい式しき
連立方程式 refers to a system of equations (often two or more) solved together, while 二元方程式 is a single equation containing two variables.
一いち次じ方ほう程てい式しき
一次方程式 is a linear equation (first-degree), which may have one or more variables; 二元方程式 specifies two variables regardless of degree.

Compound of 二元 (two unknowns) + 方程式 (equation). The term is a straightforward technical coinage in mathematics.