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Math Help - Find a, b and c

  1. #1
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    Find a, b and c

    The graph of the function f(x) = ax^2 + bx + c has a vertex at x = 1 and passes through the points (0, 1) and (-1, -8). Find a, b and c.
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  2. #2
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    Quote Originally Posted by symmetry View Post
    The graph of the function f(x) = ax^2 + bx + c has a vertex at x = 1 and passes through the points (0, 1) and (-1, -8). Find a, b and c.
    Hello,

    to calculate 3 values you need 3 equations. You know that the x-value of the vertex is -\frac{b}{2a}. So you have:

    -\frac{b}{2a}=1 \Longleftrightarrow b = -2a

    The coordinates of the given points must satisfy the equation of the function. Plug in the coordinates:

    1=a \cdot 0^2+b \cdot 0 + c \Longleftrightarrow c=1

    -8=a \cdot (-1)^2+b \cdot (-1) + c

    Solve for a, b and c. Use the method which is the most convenient for you. I've got:
    a = -3, b = 6 and c = 1

    EB
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  3. #3
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    ok

    I thank you for your help and insight.
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