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March 28, 2017

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I need help bad. Don't know which formula to use. Please explain step by step. 2x^2-12x+19. Find the interval where f is increasing and decreasing.

  • college algebra - ,

    If you are confused by formulas, it indicates you don't really understand the concepts. Let's start from scratch.

    You know the graph is a parabola, which has a vertex.
    Since the coefficient of x^2 is positive, the vertex is at the minimum value of y.

    So, left of the vertex y is decreasing, and on the right, it is increasing.

    So, where is the vertex?

    y = 2x^2 - 12x + 19
    = 2(x^2-6x) + 19
    = 2(x^2-6x+9) + 19 - 18
    = 2(x-3)^2 + 1

    So, the vertex is at (3,1)
    y decreases for x < 3
    y increases for x > 3

  • college algebra - ,

    Vertex is -b/2a

    ax^2+by+c=0

    or

    (x2-x1)/(y2-y1)

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