Solving for the y-intercept

The  exercise appears under the 8th Grade 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.Sfty1.png
 * 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.Sfty2.png

Strategies
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.