16Hit1600
Advanced MathVery hardTangent line meeting a parabola once

Advanced Math practice question

The system of equations y = x² − 4x + 3 and y = 2x − 6 has exactly one solution (x, y). What is the value of x?

Answer: 3

Setting the right sides equal: x² − 6x + 9 = 0, so (x − 3)² = 0 and x = 3.

Common wrong answers

If you answered 0
0 is y at the solution, not x.
If you answered 1
1 is a zero of the parabola but does not lie on the line (2 − 6 = −4 ≠ 0).
If you answered -3
−3 comes from a sign slip in (x − 3)².

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