vertex form parabola?

find the vertex form of the parabola

question is y=2x^2+8x-5

choose from these answers (y=2(x+2)^2-9, y=2(x+2)^2-1, y=2(x+2)^2+3, or Y=2(x+2)^2-13)

6 Answers

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  • 1 decade ago
    Best Answer

    math is fun!

  • 1 decade ago

    When your function is written in standard form

    y = ax^2 + bx + c rather than the vertex form y = a(x - h)^2 + k,

    you cannot simply look at the function and find the vertex.

    You can find the vertex of your function in two ways:

    1-Using the formula h = -b/2a

    OR

    2-By completing the square

    Using the formula is much easier.

    You function is y = 2x^2 + 8x - 5.

    In your function, a = 2 and b = 8.

    Substitute into the formula to find the x-coordinate of the vertex.

    h = -(8)/2(2)

    h = -8/4

    h = -2....This number represents the x-coordinate of your vertex.

    Substitute the value of -2 into the original function to get the y-value of the vertex.

    y = 2(-2)^2 + 8(-2) - 5

    y = 2(4) - 16 - 5

    y = 8 - 16 - 5

    y = -16 + 3

    y = -13

    I just found the x and y coordinates, which represent the h and k values in the vertex point (h, k).

    Your vertex is (-2, -13).

    You got it?

  • 1 decade ago

    y = 2(x+2)² - 13

  • DWRead
    Lv 7
    1 decade ago

    y = 2x² + 8x - 5

    = 2(x²+4x) - 5

    = 2(x²+4x +2²) - 5 - 2(2²)

    = 2(x+2)² - 13

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  • 1 decade ago

    y = 2x^2 + 8x - 5

    y = 2(x^2 + 4x + ____) - 5 - 2(___)

    y = 2(x^2 + 4x + 4) - 5 - 2(4)

    y = 2(x + 2)^2 - 13

    the last option...

    vertex is (-2, -13), shape factor = 2

  • Maria
    Lv 4
    4 years ago

    in standard form, the vertex has x value = -b/2a. From that you can find the y value. You now have (h,k) in the vertex form.

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