Skill: Write equations of lines in standard form

Explanation and Free Practice Resources

A line in standard form is represented as Ax+By=CAx+By=C, typically with integer coefficients, A≥0A\ge 0, and no common factor, so that equivalent equations describe the same set of points. The understanding includes converting from slope-intercept or point-slope form, determining an equation from a graph or given points, and recognizing horizontal and vertical lines; it is limited to linear equations in two variables and does not include parametric, vector, or higher-dimensional forms.

Detailed Explanation: Write equations of lines in standard form

Standard form for a linear equation is

Ax+By=C,Ax+By=C,

where AA, BB, and CC are integers, A≥0A\ge 0, and the coefficients have no common factor other than 11.

To convert an equation to standard form:

  1. Clear any fractions by multiplying every term by the least common denominator.
  2. Move the xx- and yy-terms to the same side.
  3. Arrange the terms as Ax+By=CAx+By=C.
  4. Make sure AA is positive and simplify if all coefficients share a common factor.

Example: Write the equation

y=23x−4y=\frac{2}{3}x-4

in standard form.

First, clear the fraction by multiplying every term by 33:

3y=2x−12.3y=2x-12.

Move the xx-term to the left side:

−2x+3y=−12.-2x+3y=-12.

Standard form requires A≥0A\ge 0. Since the coefficient of xx is negative, multiply the entire equation by −1-1:

2x−3y=12.2x-3y=12.

Therefore, the equation in standard form is

2x−3y=12.\boxed{2x-3y=12}.

Multiplying every term by the same nonzero number does not change the line, so the new equation represents the same set of points.

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