Question

A coordinate plane with a horizontal line passing through (negative 3, negative 3), (negative 3, 0) and (negative 3, 3).
Which is true of the standard form of the equation of the line graphed?

The value of A can be –1 if the value of C is 3 and the value of B is 0.
The value of A can only be 1, the value of C can only be –3, and the value of B is 0.

Answer 1

The line is vertical: x = −3. In standard form Ax + By = C (with A taken positive), this is 1x + 0y = −3. So A = 1, B = 0, C = −3. Hence the second statement is true.

(Technically −x = 3 (A = −1, B = 0, C = 3) represents the same line, but standard form convention requires A ≥ 0, so A = 1, C = −3.)