Question 173·Medium·Nonlinear Equations in One Variable; Systems in Two Variables
If the ordered pair satisfies the system of equations above, what is one possible value of ?
For systems where both equations are written as (especially a line and a parabola), the fastest approach is to set the right-hand sides equal to each other, forming a single equation in . Rearrange it into standard quadratic form, factor if possible (or use the quadratic formula), and solve for all possible -values. Finally, check that you answer exactly what is asked (here, "one possible value of ") and, if time permits, quickly plug an -value back into both equations to confirm the -values match.
Hints
Connect the two equations
The ordered pair must satisfy both equations at the same time. Since both equations are written as , what can you do with the right-hand sides of the equations?
Form a single equation in x
After you set , move all terms to one side so that the equation equals 0, then combine like terms to make a standard quadratic equation.
Solve the quadratic
You should get a quadratic of the form . Factor it by finding two numbers that multiply to and add to , then set each factor equal to 0 to find possible values of .
Desmos Guide
Graph both equations
In Desmos, enter the two equations on separate lines:
y = x^2 - 5x + 6y = 4x - 2
You will see a parabola and a straight line.
Find the intersection x-values
Zoom or pan as needed so that you can see where the parabola and the line intersect. Click (or tap) on each intersection point; Desmos will display the coordinates. The -coordinates of these intersection points are the possible values of that satisfy the system. Either -value shown there is a valid answer to the question.
Step-by-step Explanation
Set the equations equal to each other
Because both equations equal , any solution must make the right-hand sides equal:
Move everything to one side to get a quadratic equal to 0:
Now you just need to solve .
Factor the quadratic
Factor .
You need two numbers that multiply to and add to . Those numbers are and .
So the factored form is:
Use the zero-product property to find x
If , then at least one factor must be zero:
- , so
- , so
Both of these -values make the original system true. Since the question asks for one possible value of , you can give as your answer.