Find the equation of a quadratic function in standard form given that its graph contains the points. (−3, 8), (2, −12), and (1, 0)?

Update:

pls can someone else answer

3 Answers

Relevance
  • Quevvy
    Lv 4
    4 years ago

    y = ax^2+bx+c and plug in the points you have

    Start with (1,0).

    0 = a+b+c

    then (-3, 8)

    8 = 9a - 3b + c

    then (2,-12)

    -12 = 4a + 2b + c

    Use a matrix

    [1 1 1]

    [9 -3 1] * [abc] = b

    [4 2 1]

    where b =

    [0]

    [8]

    [-12]

    to get

    [abc] = A^-1*b

    to get a = -2, b = -6, c = 8

    Then we have y = -2x^2 - 6x + 8. = -2(x^2 + 3x - 4) = -2(x+4)(x-1)

    Plug in the points to double-check your work.

    [Note the negative sign that alex is missing.]

  • Jeff
    Lv 7
    4 years ago

    Hint: Let y = f(x) = Ax² + Bx + C

    Use the 3 given points to set up 3 equations in A, B, C and solve.

  • alex
    Lv 7
    4 years ago

    y=2(x-1)(y+4) = ...

Still have questions? Get your answers by asking now.