Question 145·Easy·Nonlinear Equations in One Variable; Systems in Two Variables
If satisfies the system of equations below, which of the following is a possible value of ?
For systems where one equation is linear and the other is quadratic, use substitution: solve the linear equation for one variable (or use the given solved form), substitute into the other equation to get a single-variable quadratic, then solve it by factoring or using the quadratic formula. Finally, compare the resulting -values to the answer choices, and if needed, quickly check by plugging back into both original equations to confirm they satisfy the system.
Hints
Connect the two equations
You know both and . How can you use the expression for from the second equation inside the first equation?
Form a single equation in one variable
After you substitute into , rearrange the equation so that everything is on one side and the other side is .
Solve the quadratic
Once you have a quadratic equation in , try factoring it. If it factors into two binomials, set each factor equal to zero to find possible -values, then see which one appears in the choices.
Desmos Guide
Graph both equations as functions
In Desmos, enter the two equations as functions: y = x^2 and y = (x + 1)/2. These are equivalent to the system and .
Find the intersection points
Look for the points where the graphs of and intersect. Click on each intersection point that Desmos shows and note the -coordinates.
Match with the answer choices
Compare the -coordinates of the intersection points to the answer options and identify which option matches one of those -values.
Step-by-step Explanation
Use substitution to get one equation in terms of
You are given the system
Because , substitute for in the first equation.
So becomes:
Rewrite as a standard quadratic equation
To solve for , move all terms to one side so the equation equals .
Starting with
subtract and from both sides:
This is a quadratic equation in standard form .
Factor the quadratic
Now factor .
We look for two binomials of the form that multiply to give .
Trying :
So the factored form is
Solve for and match with the answer choices
Use the zero product property: if , then either or .
Solve each:
- From : , so .
- From : .
The possible -values are and . Among the answer choices , the only one that matches a solution is , so the correct answer is .