Question 23·Medium·Nonlinear Equations in One Variable; Systems in Two Variables
Which ordered pair is the solution to the given system of equations?
For systems with a line and a parabola, use substitution by setting the two expressions for y equal to each other, then simplify to a quadratic equation. Factor or use the quadratic formula to find the x-value(s), substitute each into either original equation to get the corresponding y-value(s), and finally select the ordered pair that appears in the choices. This approach is usually faster and less error-prone than guessing points from the options.
Hints
Use the fact that both y-values are equal
At the solution, the same point lies on both graphs, so the y-values from and must be equal for that x. How can you write an equation that shows this?
Create and solve a quadratic equation
After setting equal to , move all terms to one side so you have an equation equal to 0. Can you factor the resulting quadratic?
Substitute back to find y
Once you find the value of that satisfies the quadratic, plug it into either original equation (the line or the parabola) to compute the corresponding y-value.
Match with the answer choices
Use the x and y you found to form an ordered pair and then see which choice matches that exact pair.
Desmos Guide
Enter both equations
In Desmos, type y = x^2 + 2x + 3 on one line and y = 4x + 2 on another line so both graphs (a parabola and a line) appear.
Find the intersection point
Look for the point where the line and the parabola cross. Tap or click on the intersection point; Desmos will display its coordinates . These coordinates are the solution to the system.
Compare with answer choices
Match the x- and y-coordinates of that intersection point with the listed answer options to see which ordered pair is correct.
Step-by-step Explanation
Set the equations equal
At the solution, both equations have the same x and the same y, so the right-hand sides must be equal.
Now move all terms to one side to get a standard quadratic equation.
Form and factor the quadratic
Subtract from both sides:
Factor the quadratic:
So there is only one solution for .
Solve for x
From , we get:
Now use this x-value in either original equation to find the matching y-value.
Find y and identify the ordered pair
Substitute into the linear equation :
So the solution to the system is the ordered pair , which corresponds to answer choice C.