The Solving for the y-intercept exercise used to appear under the Algebra I Math Mission. This exercise finds the y-intercepts on linear graphs.

Types of Problems

There are two types of problems in this exercise:

  1. Find the y-intercept of the equation: This problem provides a linear equation written in standard form. The student is asked to find the y-intercept of the equation and provide the answer in an ordered pair slot.

    Find the y-intercept of the equation

  2. Find the b in the formula: This problem provides an equation in slope-intercept form (with b unknown) and a point. The student will use the point to find the y-intercept of the line.

    Find the b in the formula


Solving linear equations and substituting values for variables are needed to perform this exercise in the standard way. Graphing could be used to avoid these skills.

  1. The y-intercept is found by replacing x with zero and solving.
  2. Since the Find the y-intercept of the equation problem is practically the same, dividing the isolated number on the right by the coefficient to the y will always provide the single number that needs to be inserted.
  3. On the Find the b in the formula problem, If the point is (x,y) and the equation is y=mx+b, the answer will be y-mx.

Calculator Programs for TI83/84 series

For the Find the b in the formula problem:

Prompt X,Y,M
Disp Y-MX>Frac

Real-life applications

  1. Problems like this occur on SATs and other standardized tests.
  2. Linear models are common in business and the sciences and the y-intercept often provides information about the model such as initial values.

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