LUANDATO wrote:What is the equation of ine m?
(1) The slope of line m is 2.
(2) The x-intercept of line m is 3.
Target question: What is the equation of line m?
IMPORTANT: For many coordinate geometry Data Sufficiency questions, we are often checking to see whether the statements "lock" a particular line/curve into having just one possible location.
This concept is discussed in much greater detail in this video:
https://www.gmatprepnow.com/module/gmat- ... cy?id=1103
Statement 1: The slope of line m is 2
There are MANY different lines we can draw with slope 2.
Just draw a line with slope 2 and then move it up and down wherever you want, and the slope will still be 2.
Since statement 1 does not LOCK IN the placement of line m, it is NOT SUFFICIENT
Statement 2: The x-intercept of line m is 3
There are MANY different lines we can draw with an x-intercept of 3.
Just draw a line through the point (3,0) and spin it around that point, and the x-intercept will still be 3.
Since statement 2 does not LOCK IN the placement of line m, it is NOT SUFFICIENT
Statements 1 and 2 combined
Take our line with slope 2 (from statement 1).
Notice that, if we say this line must also pass through the point (3,0), then there is ONLY ONE such possible line.
Since the combined statements LOCK IN the placement of line m, they are SUFFICIENT
ASIDE: Are we going to actually find the equation of line m? No! We need only recognize that we COULD find the equation (since there's only 1 line that meets the given conditions). Finding the actual equation is a waste of valuable time.
Answer = C
Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
