Equation of a Line

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Almost any student who has studied triangles has heard of Pythagoras (the author of the Pythagorean Theorem). He lived from roughly 569 B.C. to 500 B.C. and is considered by many to have been the first pure mathematician. In addition to mathematics, Pythagoras also studied music and religion. He is a fascinating historical figure and would make a great "Excellent Example" for your essay. You can lean more about Pythagoras here. 

6/26 Equation of a line

Read the following SAT test question and then select the correct answer choice.

As always, remember to follow the Knowsys method for math. Read the problem carefully and identify the bottom line (what you are looking for). Then, consider your options. How could you solve it? How should you solve it? Next, attack the problem using the method that you selected. Finally, loop back and verify that your answer matches the bottom line. Do not forget the last step. If the problems asks for what "must be false" and you choose an answer that "could be true" you will lose points (even if you solved the equation correctly).

If the graph of the function f is a line with a slope of 2, which of the following could be the equation of f?

Whenever a problem seems straightforward and simple (as this one does), make sure that you read it carefully. Also, look at where in the section the problem appears. If it is one of the last problems in the section, it's probably a hard problem (so if it looks easy, you probably have fallen for a trap). In this case, this problem really is as easy and straightforward as it seems. As long as you remember the slope intercept form of a line, you should have no trouble selecting the correct answer.

(A) f(x) = 4x-2

(B) f(x) = 2x+4

(C) f(x) = -2x-2
(D) f(x) = 1/2x +2
(E) f(x) = -1/2x+1/2

If you remember the slope intercept form of a line (y=mx+b where m is the slope of the line and b is the y intercept) then this problem is very simple. You simply need to look through the answers and select the answer choice with a slope of 2. (A) is incorrect because the slope of the line is 4. (B) works because the slope is 2. (C) has a slope of -2, (D) has a slope of 1/2, and (E) has a slope of -1/2.


The correct answer choice is (B).

On sat.collegeboard.com 64% of the responses were correct.

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