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jay
jay asked in Science & MathematicsMathematics · 8 years ago

Factor 3x^2+15x-42?Explain?

I'm stuck! Please explain the answer

3 Answers

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  • ranjankar
    Lv 7
    8 years ago
    Favorite Answer

    3 ( x^2 + 5x - 14)

    3 ( x^2 -2x +7x -14 )

    3 ( x ( x-2) +7( x-2) )

    3 ( x+7) ( x-2) ANSWER

  • Niall
    Lv 7
    8 years ago

    Before doing anything, always look for a common factor. Take out 3 as a common factor:

    3(x^2 + 5x - 14)

    Factor the trinomial:

    3(x + 7)(x - 2)

  • ?
    Lv 7
    8 years ago

    3x^2+15x-42 = 3(x^2+5x-14) [factoring out 3]

    3x^2+15x-42 = 3(x^2+(m+(5-m))x+m(-14/m)) [where 1:m = (5-m):-14]

    so m = -2 (where 1:-2 = 7:-14), or m = 7 (where 1:7 = -2:-14) and hence

    3x^2+15x-42 = 3(x-2)(x+7)

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