SAT Math · Systems of equations in two variables · medium
How many real solutions does the system y = -x² + 4x + 1 and y = x - 2 have?
How many real solutions does the system and have?
Answer and explanation
Answer: B: 2
Set the two expressions for equal: . Move everything to one side: . The discriminant is . Since it is positive, the quadratic has two distinct real roots, so the parabola and the line meet at 2 points, choice B. Choice A (0) would need a negative discriminant. Choice C (1) would need a discriminant of zero, meaning tangency. Choice D (4) is impossible, since a line and a parabola intersect at most twice.
More Systems of equations in two variables questions
- Question 35 · hardFor what value of k is the line y = 2x + k tangent to the parabola y = x² - 4x + 7?
- Question 64 · hardA circle is defined by x² + y² = 25. A line given by y = x + 1 intersects the circle at two…
- Question 96 · mediumIf x² + y = 10 and x² - y = 4, what is the value of y?
- Question 98 · mediumThe equations x² - 5x + 6 = 0 and x² + kx - 12 = 0 share x=3 as a common root. What is the value…
- Question 114 · hardThe circle x² + y² = 8 is tangent to the line y = x + k for a positive value of k. What is that…
- Question 115 · mediumThe graphs of y = x² and y = 3x + 4 intersect at two points. What is the sum of the x-coordinates…
Learn the method behind questions like this one
The SAT Math course teaches each tested skill through lessons, step-by-step solutions to sample problems, the complete study guide and full-length practice tests.