Cracking The SAT Premium

Here’s an example:

4.

Which   of  the following   could   be  the equation    of  the line    represented in  the graph   above?

A) y    =   2x  +   4

B) y    =   2x  −   4

C) y    =   –2x −   1

D) y    =   –2x +   4

Here’s How to Crack It

Remember that the equation of a line is y = mx + b, where m is the slope and b is the y-intercept. Look at
the graph and think about what the equation should look like. Since the line is sloping downward, it
should have a negative slope, so you can eliminate (A) and (B). Next, since the line has a positive y-
intercept, you can eliminate (C), and only (D) remains.

Equation of a Line—Standard Form

Another way the equation of a line can be written is the standard form of Ax + By = C, where A, B, and C
are constants and A and B do not equal zero. The test writers will sometimes present equations in this
form in the hopes that you will waste time putting it in slope-intercept form. If you know what to look for,
the standard form can be just as useful as the slope-intercept form.

In  standard    form    Ax  +   By  =   C:

The slope   of  the line    is  –   .

The y-intercept of  the line    is  .

The x-intercept of  the line    is  .