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Consider the polynomials \(f(x) = ax^2 + bx + c\), where \(a > 0, b, c\) are real, \(g(x) = -2x\). If \(f(x)\) cuts the x-axis at \((-2, 0)\) and \(g(x)\) passes through \((a, b)\), then the minimum…

Question and options

Consider the polynomials f(x)=ax2+bx+cf(x) = ax^2 + bx + c, where a>0,b,ca > 0, b, c are real, g(x)=−2xg(x) = -2x. If f(x)f(x) cuts the x-axis at (−2,0)(-2, 0) and g(x)g(x) passes through (a,b)(a, b), then the minimum value of f(x)+9a+1f(x) + 9a + 1 is
  1. 0
  2. 1
  3. 2
  4. 3

Answer and explanation

Correct answer: B - 1
g passes through (a,b): b=-2a. f(-2)=0: 4a-2b+c=0 -> 8a+c=0 -> c=-8a. f = a(x^2-2x-8), minimum at x=1 equals -9a. So min of f+9a+1 = 1.

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