Advanced MathHardCompleting a perfect-square trinomial
Advanced Math practice question
The trinomial x² + bx + 49 is a perfect square for a positive constant b. What is the value of b?
Answer: 14
A perfect square (x + 7)² has middle coefficient 2 · 7 = 14.
Common wrong answers
- If you answered 7
- 7 is the square root of 49; the middle coefficient doubles it.
- If you answered 49
- 49 is the constant term; b = 2√49 = 14.
- If you answered 98
- 98 is 2 · 49; the doubling applies to √49 = 7.
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