What is the standard form of a linear equation?

• A. ax + by = c
• B. y = mx + b
• C. x^2 + y^2 = r^2
• D. y = ax^2 + b

Answer: (B)

The key idea is how linear equations are written. The standard form writes the equation with x and y on one side and a constant on the other: Ax + By = C, where A, B, and C are constants (not both A and B zero). This arrangement makes it easy to read off intercepts and to combine equations in systems.

The option that places y in terms of x, as y = mx + b, is slope-intercept form. It’s very handy for graphing because it shows the slope m and the y-intercept b directly, but it isn’t the standard form. The other options describe shapes that aren’t lines (a circle and a quadratic curve). So the standard form for a linear equation is Ax + By = C, not y = mx + b.