All Leaving Cert Mathematics posts
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    functions question on mock paper. Leeo

    Hi, anyone know how to find a function when you're given the quadratic graph?

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      aoifemcgrath96

      find out where it crosses the x axis, for example x=2 and x=-3 these are the roots

      x-2 and x+3 are your factors, multiple these out and you'll be left with f(x)=x^2 + x -6

      hope that answers your question! :)

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      themathstutor.ie

      Agreed. And in the above example, the graph should cross the y-axis at -6, so that's a good check to make too.

      If it only touches the x-axis (without crossing it), for example if it touches the x-axis at (3,0), then the factors are identical. So, (x-3)(x-3), which simplifies to x^2 -6x + 9

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      eimearnr

      For the mock question we picked values then using differentiation found out whether it was rising or falling , you can pick the grah fro that

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      eimearnr

      For the mock question we picked values then using differentiation found out whether it was rising or falling , you can pick the grah fro that

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