SAT Math Practice Question #1157 (Hard (800)) | Test Citadel
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SAT Math Difficulty: Hard (800)

Digital SAT Math Practice Question #1157

Test your problem-solving accuracy on this official-caliber item. Select an answer choice to check your reasoning instantly.

The graph of the quadratic function \( f(x) = ax^2 + bx + c \) in the \( xy \)-plane passes through the point \( (0, 18) \) and has a vertex at \( (3, 0) \). If the line \( y = mx + k \) is tangent to \( f(x) \) at \( x = 1 \), what is the value of \( m + k \)?
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Socratic AI Engine Step-by-Step Derivation
0ms Precomputed
Tactical Insight (Hint 1)

Express the parabola in vertex form f(x) = a(x - h)^2 + k. Use the y-intercept to find 'a', then calculate the slope at x = 1.

Elimination Framework (Hint 2)

Desmos Shortcut: Type y = 2(x - 3)^2 into Desmos. Then type y = -8x + 16 to observe the exact single point of tangency at (1, 8).

Masterclass Solution & Distractor Trap Analysis

Since the vertex is at (3,0), the function is f(x) = a(x - 3)^2. Given f(0) = 18, a(0 - 3)^2 = 18 implies 9a = 18, so a = 2. Thus, f(x) = 2(x - 3)^2 = 2x^2 - 12x + 18. At x = 1, f(1) = 2(1 - 3)^2 = 8, so the point of tangency is (1, 8). The...

Distractor Analysis: Trap choice eliminates careless test-takers who confuse roots with coordinates...

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