GMAT Math : DSQ: Calculating the equation of a line
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Example Questions
Example Question #1 : Dsq: Calculating The Equation Of A Line
Find the equation of linear function 
I)
II) 
Statement II is sufficient to answer the question, but Statement I is not sufficient to answer the question.
Statement I is sufficient to answer the question, but Statement II is not sufficient to answer the question.
Both statements are needed to answer the question.
Either statement is sufficient to answer the question.
Neither statement is sufficient to answer the question. More information is needed.
Both statements are needed to answer the question.
To find the equation of a linear function, we need some combination of slope and a point.
Statement I gives us a clue to find the slope of the desired function. It must be the opposite reciprocal of the slope of 
Statement II gives us a point on our desired function, 
Using slope-intercept form, we get the following:
So our equation is as follows
Example Question #2 : Other Lines
There are two lines in the xy-coordinate plane, a and b, both with positive slopes. Is the slope of a greater than the slope of b?
1)The square of the x-intercept of a is greater than the square of the x-intercept of b.
2) Lines a and b have an intersection at
Statement 2 alone is sufficient.
Statement 1 alone is sufficient.
Together the two statements are sufficient.
Neither of the statements, together or separate, is sufficient.
Either of the statements is sufficient.
Neither of the statements, together or separate, is sufficient.
Given that the square of a negative is still positive, it is possible for a to have an x-intercept that is negative, while still having a positive slope. The example above shows how the square of the x-intercept for line a could be greater, while having still giving line a a slope that is less than that of b.
Example Question #651 : Geometry
Line j passes through the point 
1) Line j is perpindicular to the line defined by
2) Line j has an x-intercept of
Statement 1 alone is sufficient.
Statement 2 alone is sufficient.
Together, the two statements are sufficient.
Neither of the statements, separate or together, is sufficient.
Either of the statements is sufficient.
Either of the statements is sufficient.
Either statement is sufficient.
Line j, as a line, has an equation of the form
Statement 1 gives the equation of a perpindicular line, so the slopes of the two lines are negative reciprocals of each other:
Statement 2 allows the slope to be found using rise over run:
Then, since the x-intercept is known:
Example Question #3 : Dsq: Calculating The Equation Of A Line
Find the equation for linear function 
I) 
II)
Neither statement is sufficient to answer the question. More information is needed.
Statement I is sufficient to answer the question, but statement II is not sufficient to answer the question.
Either statement is sufficient to answer the question.
Statement II is sufficient to answer the question, but statement I is not sufficient to answer the question.
Both statements are needed to answer the question.
Both statements are needed to answer the question.
Find the equation for linear function p(x)
I) 
II)
To begin:
I) Tells us that p(x) must have a slope of 16
II) Tells us a point on p(x). Plug it in and solve for b:
Example Question #764 : Data Sufficiency Questions
Give the equation of a line.
Statement 1: The line interects the graph of the equation 
Statement 2: The line interects the graph of the equation 
BOTH STATEMENTS TOGETHER provide sufficient information to answer the question, but NEITHER STATEMENT ALONE provides sufficient information to answer the question.
BOTH STATEMENTS TOGETHER do NOT provide sufficient information to answer the question.
STATEMENT 2 ALONE provides sufficient information to answer the question, but STATEMENT 1 ALONE does NOT provide sufficient information to answer the question.
STATEMENT 1 ALONE provides sufficient information to answer the question, but STATEMENT 2 ALONE does NOT provide sufficient information to answer the question.
EITHER STATEMENT ALONE provides sufficient information to answer the question.
BOTH STATEMENTS TOGETHER do NOT provide sufficient information to answer the question.
Assume both statements to be true. Then the line shares its 
making the 
The common 
The parabola therefore has two 
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