SAT Math Multiple Choice Question 336: Answer and Explanation
6. At what value(s) of x do the graphs of y = -2x + 1 and y = 2x2 + 5x + 4 intersect?
Correct Answer: B
Category: Passport to Advanced Math / Quadratics
Strategic Advice: Although this question asks where the graphs intersect, it is not necessary to actually graph them. Understanding the connection between graphing the equations and the algebra behind the graphs will save valuable time on Test Day.
Getting to the Answer: The point(s) at which the two graphs intersect are the points where the two equations are equal to each other. So, set the equations equal and use algebra to solve for x. Because the question only asks for the x-values, you don't need to substitute the results back into the equations to solve for y.
Now that the equation is factored, use the Zero-Product Property to solve for x: