P1.2.1 - Equation of a straight line

Equation of a straight line, To include: including the forms (i) the equation of a line through two given points y − y = m(x − x) and 1 1 (ii) the equation of a line parallel (or perpendicular) to a ax + by + c = 0. given line through a given point.; For example, the line perpendicular to the line 3x + 4y = 18 through the point (2, 3) has equation y − 3 = 4 (x − 2).

Use equation of a straight line to connect the rule to the data and decision in the question.

This matters because equation of a straight line determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply equation of a straight line to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: use the formula and units given in the question, show the substitution and interpret the result; the calculation alone is not the conclusion.