SAT 代数・上級数学 練習問題

Algebra / Linear Equations Two Variables

Linear Equations, Intercepts, and Points

Two-variable linear equations can be interpreted through intercepts, points on a graph, and context equations with two quantities.

Least you need to know

  • To find the $x$-intercept, set $y=0$.
  • To find the $y$-intercept, set $x=0$.
  • A point lies on a graph if its coordinates make the equation true.

Key notation

  • $3x+4y=24$ — A linear equation whose intercepts can be found by setting one variable to 0

Worked example

  • For $2x+5y=20$, the $x$-intercept occurs when $y=0$.
  • Then $2x=20$, so $x=10$.

Common mistakes

  • Intercept questions ask for a coordinate or a coordinate value.
  • Substitute both coordinates when checking whether a point lies on a graph.

How to recognize it

  • The problem asks about an intercept.
  • The problem gives a point and asks for a parameter.
  • The equation contains both $x$ and $y$.

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