All GMAT Math Resources
Example Questions
Example Question #61 : Coordinate Geometry
has as its graph a vertical parabola on the coordinate plane. You are given that , but you are given neither nor .
Which of the following can you determine without knowing the values of and ?
I) Whether the curve opens upward or opens downward
II) The location of the vertex
III) The location of the -intercept
IV) The locations of the -intercepts, if there are any
V) The equation of the line of symmetry
II and V only
III only
I only
V only
III and IV only
I only
I) The orientation of the parabola is determined solely by the value of . Since , the parabola can be determined to open upward.
II and V) The -coordinate of the vertex is ; since you are not given , you cannot find this. Also, since the line of symmetry has equation , for the same reason, you cannot find this either.
III) The -intercept is the point at which ; by substitution, it can be found to be at . is unknown, so the -intercept cannot be found.
IV) The -intercept(s), if any, are the point(s) at which . This is solvable using the quadratic formula
Since all three of and must be known for this to be evaluated, and only is known, the -intercept(s) cannot be identified.
The correct response is I only.
Example Question #1 : How To Graph A Quadratic Function
The parabolas of the functions and on the coordinate plane have the same vertex.
If we define , which of the following is a possible equation for ?
None of the other responses gives a correct answer.
The eqiatopm of is given in the vertex form
,
so the vertex of its parabola is . The graphs of and are parabolas with the same vertex, so they must have the same values for and .
For the function , and .
Of the five choices, the only equation of that has these same values, and that therefore has a parabola with the same vertex, is .
To verify, graph both functions on the same grid.
Example Question #1 : Graphing A Line
A line has slope . Which of the following could be its - and -intercepts, respectively?
and
and
None of the other responses gives a correct answer.
and
and
None of the other responses gives a correct answer.
Let and be the - and -intercepts, respectively, of the line. Then the slope of the line is , or, equilvalently, .
We do not need to find the actual slopes of the four choices if we observe that in each case, and are of the same sign. Since the quotient of two numbers of the same sign is positive, it follows that is negative, and therefore, none of the pairs of intercepts can be those of a line with positive slope .
Example Question #2 : Graphing A Line
A line has slope . Which of the following could be its - and -intercepts, respectively?
and
and
and :
None of the other responses gives a correct answer.
and
and
Let and be the - and -intercepts, respectively, of the line. Then the slope of the line is , or, equilvalently, .
We can examine the intercepts in each choice to determine which set meets these conditions.
and :
Slope:
and
Slope:
and
Slope:
and
Slope:
and comprise the correct choice.
Example Question #1011 : Gmat Quantitative Reasoning
Which of the following equations can be graphed with a line perpendicular to the green line in the above figure, and with the same -intercept?
The slope of the green line can be calculated by noting that the - and -intercepts of the line are, respectively, and . If and be the - and -intercepts, respectively, of a line, the slope of the line is . This makes the slope of the green line .
Any line perpendicular to this line must have as its slope the opposite reciprocal of this, or . Since the desired line must also have -intercept , the equation of the line, in point=slope form, is
which can be simplified as
Example Question #4 : Graphing A Line
A line passes through the vertex and the -intercept of the parabola of the equation . What is the equation of the line?
To locate the -intercept of the equation , substitute 0 for :
The -intercept of the parabola is .
The vertex of the parabola of an equation of the form has -coordinate . Here, we substitute , to obtain -coordinate
.
To find the -coordinate, substitute this for :
The vertex is .
The line includes points and ; apply the slope formula:
The slope is , and the -intercept is ; in the slope-intercept form , substitute for and . The equation of the line is .
Example Question #5 : Graphing A Line
Give the equation of a line with undefined slope that passes through the vertex of the graph of the equation .
A line with undefined slope is a vertical line, and its equation is for some , so the -coordinate of all points it passes through is . If it goes through the vertex of a parabola , then the line has the equation . Therefore, all we need to find is the -coordinate of the vertex of the parabola.
The vertex of the parabola of the equation has as its -coordinate , which, for the parabola of the equation , can be found by setting :
The desired line is .
Example Question #2 : Graphing A Line
A line has slope 4. Which of the following could be its - and -intercepts, respectively?
and
and
None of the other responses gives a correct answer.
and
and
and
Let and be the - and -intercepts, respectively, of the line. Then the slope of the line is , or, equilvalently, .
We can examine the intercepts in each choice to determine which set meets these conditions.
and
Slope:
and
Slope:
and
Slope:
and
Slope:
and comprise the correct choice, since a line passing through these points has the correct slope.
Example Question #3 : Graphing A Line
The graph of the equation shares its -intercept and one of its -intercepts with a line of negative slope. Give the equation of that line.
The -intercept of the line coincides with that of the graph of the quadratic equation, which is a parabola; to find the -intercept of the parabola, substitute 0 for in the quadratic equation:
The -intercept of the parabola, and of the line, is .
The -intercept of the line coincides with one of those of the parabola; to find the -intercepts of the parabola, substitute 0 for in the equation:
Using the method, split the middle term by finding two integers whose product is and whose sum is ; by trial and error we find these to be and 4, so proceed as follows:
Split:
or
The -intercepts of the parabola are and , so the -intercept of the line is one of these. We examine both possibilities.
If and be the - and -intercepts, respectively, of the line, then the slope of the line is , or, equivalently,
If the intercepts are and , the slope is ; if the intercepts are and , the slope is . Since the line is of negative slope, we choose the line of slope ; since its -intercept is , then we can substitute in the slope-intercept form of the line, , to get the correct equation, .
Example Question #8 : Graphing A Line
Which of the following equations can be graphed with a line parallel to the green line in the above figure?
None of the other choices gives a correct answer.
If and be the - and -intercepts, respectively, of a line, the slope of the line is .
The - and -intercepts of the line are, respectively, and , so , and consequently, the slope of the green line is . A line parallel to this line must also have slope .
Each of the equations of the lines is in slope-intercept form , where is the slope, so we need only look at the coefficients of . The only choice that has as its -coefficient is , so this is the correct choice.