All SSAT Upper Level Math Resources
Example Questions
Example Question #12 : How To Find The Equation Of A Curve
A horizontal parabola on the coordinate plane has -intercept ; one of its -intercepts is .
Give its equation.
Insufficient information is given to determine the equation.
Insufficient information is given to determine the equation.
The equation of a horizontal parabola, in standard form, is
for some real .
is the -coordinate of the -intercept, so , and the equation is
Set :
However, no other information is given, so the values of and cannot be determined for certain. The correct response is that insufficient information is given.
Example Question #13 : How To Find The Equation Of A Curve
A vertical parabola on the coordinate plane includes points and .
Give its equation.
The standard form of the equation of a vertical parabola is
If the values of and from each ordered pair are substituted in succession, three equations in three variables are formed:
The system
can be solved through the elimination method.
First, multiply the second equation by and add to the third:
Next, multiply the second equation by and add to the first:
Which can be divided by 3 on both sides to yield
Now solve the two-by-two system
by substitution:
Back-solve:
Back-solve again:
The equation of the parabola is therefore
.
Example Question #14 : How To Find The Equation Of A Curve
A vertical parabola on the coordinate plane shares one -intercept with the line of the equation , and the other with the line of the equation . It also passes through . Give the equation of the parabola.
The correct answer is not among the other responses.
First, find the -intercepts—the points of intersection with the -axis—of the lines by substituting 0 for in both equations.
is the -intercept of this line.
is the -intercept of this line.
The parabola has -intercepts at and , so its equation can be expressed as
for some real . To find it, substitute using the coordinates of the third point, setting :
.
The equation is , which, in standard form, can be rewritten as:
Example Question #15 : How To Find The Equation Of A Curve
A horizontal parabola on the coordinate plane includes points , and .
Give its equation.
The standard form of the equation of a horizontal parabola is
If the values of and from each ordered pair are substituted in succession, three equations in three variables are formed:
The three-by-three linear system
can be solved by way of the elimination method.
can be found first, by multiplying the first equation by and add it to the second:
Substitute 5 for in the last two equations to form a two-by-two linear system:
The system
can be solved by way of the substitution method;
Substitute 2 for in the top equation:
The equation is .
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