Two-Variable Equations
Aligned to A-CED.A.2 — Common Core State Standards for Mathematics.
What this lesson teaches
Many situations relate two quantities; write an equation using both variables and graph it, labeling the axes and choosing a scale that fits the data.
Worked example
A gym charges $20 to join plus $5 per visit. Total cost y for x visits is y = 5x + 20. The y-intercept 20 is the join fee, and the slope 5 is the cost per visit.
Practice questions
- Write an equation for a taxi that charges $3 plus $2 per mile.
- A tank holds 500 L and drains 25 L per minute. Write y in terms of x minutes.
- For y = 4x + 10, find y when x = 3.
Watch the lesson
Every lesson comes with a video taught in English and Spanish — the same video the QR code in the printed workbook opens.
▶ Watch this lessonEn español
Ecuaciones de Dos Variables
Muchas situaciones relacionan dos cantidades; escribe una ecuación con ambas variables y grafícala, rotulando los ejes y eligiendo una escala que se ajuste a los datos.
Ejemplo: Un gimnasio cobra $20 de inscripción más $5 por visita. El costo total y para x visitas es y = 5x + 20. La intersección con el eje y, 20, es la inscripción, y la pendiente 5 es el costo por visita.
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