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f(x)=x^(2)-4x-1
Which of the following is an equivalent form of the function 
f in which the minimum value of 
f appears as a constant or coefficient?
Choose 1 answer:
(A) 
f(x)=-(x-2)^(2)-5
(B) 
f(x)=(x-4)(x-1)
(C) 
f(x)=(x-2)^(2)-5
(D) 
f(x)=x(x-4)-1

f(x)=x24x1 f(x)=x^{2}-4 x-1 \newlineWhich of the following is an equivalent form of the function f f in which the minimum value of f f appears as a constant or coefficient?\newlineChoose 11 answer:\newline(A) f(x)=(x2)25 f(x)=-(x-2)^{2}-5 \newline(B) f(x)=(x4)(x1) f(x)=(x-4)(x-1) \newline(C) f(x)=(x2)25 f(x)=(x-2)^{2}-5 \newline(D) f(x)=x(x4)1 f(x)=x(x-4)-1

Full solution

Q. f(x)=x24x1 f(x)=x^{2}-4 x-1 \newlineWhich of the following is an equivalent form of the function f f in which the minimum value of f f appears as a constant or coefficient?\newlineChoose 11 answer:\newline(A) f(x)=(x2)25 f(x)=-(x-2)^{2}-5 \newline(B) f(x)=(x4)(x1) f(x)=(x-4)(x-1) \newline(C) f(x)=(x2)25 f(x)=(x-2)^{2}-5 \newline(D) f(x)=x(x4)1 f(x)=x(x-4)-1
  1. Completing the Square: We need to complete the square to rewrite the function in vertex form, which will reveal the minimum value of the function.\newlinef(x)=x24x1f(x) = x^2 - 4x - 1\newlineTo complete the square, we take the coefficient of xx, which is 4-4, divide it by 22, and square it. This gives us (4/2)2=4(-4/2)^2 = 4.\newlineWe add and subtract this value inside the function to complete the square.\newlinef(x)=(x24x+4)41f(x) = (x^2 - 4x + 4) - 4 - 1
  2. Rewriting the Function: Now we can rewrite the function as a perfect square trinomial minus the constants we've added and subtracted.\newlinef(x)=(x2)25f(x) = (x - 2)^2 - 5\newlineThis is the vertex form of the quadratic function, where the vertex (h,k)(h, k) represents the minimum point if the parabola opens upwards (which it does since the coefficient of the x2x^2 term is positive).
  3. Comparing with Answer Choices: We compare the vertex form we found with the given answer choices to find the matching form.\newline(A) f(x)=(x2)25f(x) = -(x - 2)^2 - 5 (This is incorrect because it has a negative sign before the squared term, which would indicate a maximum value, not a minimum.)\newline(B) f(x)=(x4)(x1)f(x) = (x - 4)(x - 1) (This is factored form, not vertex form.)\newline(C) f(x)=(x2)25f(x) = (x - 2)^2 - 5 (This matches the form we found and shows the minimum value as a constant.)\newline(D) f(x)=x(x4)1f(x) = x(x - 4) - 1 (This is expanded form, not vertex form.)

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