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Graphing Equations

Link of the Day

Most of you are probably familiar with the book Alice in Wonderland. The story is a fantastic and whimsical one, but on the surface it would seem to be nothing but nonsense written for children. However, as with most literary works that stand the test of time there is more to Alice in Wonderland than meets the eye. Alice in Wonderland was written by Charles Dodgeson (who used the pen name Lewis Carroll). Dodgeson was a math teacher in Oxford, England, and many of the strange things that happen to Alice during her adventures in Wonderland were actually written as satire to refer to and criticize the newly emerging mathematical theories. You can read more about the math behind Alice in Wonderland here.

Mathematics: Graphing Equations

Always follow the Knowsys Method for math problems. It will save you time not only on the SAT, but also on math tests and quizzes in your school classes. Read the question carefully and identify the bottom line. Assess your options. Ask what you could do and then what you should do, and solve the problem quickly and efficiently once you have decided on a strategy. Finally, loop back to double check that you answered the question correctly.

What is the equation of the line parallel to the x-axis and four units above the x-axis?


Remember, the first step to any problem is to read it carefully. That seems obvious, but it is often where students make their first mistake. When you glance at this question, it may seem a little confusing at first. If that is the case, make sure that you take your time and reread the question carefully. We are trying to find the equation of a line that is parallel to the x-axis. That means that the line will run horizontally. In other words, the slope (which is the rise over the run) will be zero. The line will also be 4 units above the x-axis. That means that the y intercept will be 4. At this point we could check each answer and graph the different equations until we find one that fits. That might seem like a tempting choice but remember, we want to solve the problem as quickly as possible (to leave time for the other problems in the section). It would be much faster to remember the slope intercept form of the equation for a line, y = mx + b. In this case the slope (m) is zero and the y-intercept (b) is 4. Our equation, then, must be y = 4. Now we look at the answers below to find the one that matches our prediction.

(A) x = 4


(B) x = -4


(C) y = -4


(D) y = 0


(E) y = 4

We can see that E matches our prediction exactly, and that is the correct answer.

On sat.collegeboard.org, 66% of responses were correct.

For more help with math, visit www.myknowsys.com!