Anonymous
Anonymous asked in 科學及數學數學 · 1 decade ago

f4 maths (1 quesion)

f(x)=-3x2-2x+1

找這三個:

the line of symmetry

the vertex

the y-intercept

1 Answer

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  • 1 decade ago
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    f(x) = -3x2 - 2x + 1

    y-intercept = f(0) = +1

    Use completing square method,

    f(x) = -3 (x2 + 2x/3) + 1

    = -3 (x2 + 2x/3 + 1/9 - 1/9) + 1

    = -3 (x2 + 2x/3 + 1/9) + 1/3 + 1

    = -3 (x2 + 2x/3 + 1/9) + 4/3

    = -3 (x + 1/3)2 + 4/3

    Line of symmetry : x = -1/3

    vertex = (-1/3, 4/3)

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