What is the slope of my line?

umaa · Posted: Mon Jul 21, 2008 6:12 am Post subject: What is the slope of my line?

GMAT Prep- Data Sufficiency: What is the slope of my line?

1. My line intersects y=3x+1 at (1,4)

2. My line is perpendicular to y=3x+1

A. Statement 1 ALONE is sufficient, but statement 2 alone is not sufficient

B. Statement 2 ALONE is sufficient, but statement 1 alone is not sufficient.

C. BOTH statements TOGETHER are sufficient, but NEITHER statement alone is sufficient.

D. EACH statement ALONE is sufficient

E. Statements 1 and 2 TOGETHER are NOT sufficient

Please let me know the answer and explanation.

pepeprepa · Posted: Mon Jul 21, 2008 6:41 am Post subject:

With 1), you can draw y=3x+1 with two points (-1/3;0) and (0;1).
But you have only one poine of your line, you cannot know its slope.

With 2), you can draw y=3x+1 with two points (-1/3;0) and (0;1). You can see that y=3x+1 has a positive slope. Given that your line is perpendicular, your line has a negative slope.
I don't know if it is a theorema: " 2 lines are perpendicular, if you know the slope of 1 line, the slope of the other line is the opposite of the first line "

B