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    http://prntscr.com/b0ol03

    The numerator I can do but I can't do the denominator when they add the 2 to the x^2 i get confused and have no idea how to do it. Can anyone explain to me how to do.

    Thanks
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    what 2 numbers multiply to give -30 and add to give -7?
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    Factorise 2x^2-7x-15.

    Need two numbers whose product is a*c = 2*-15=-30 and sum is b= -7 (from ax^2+bx+c).
    -10 and +3 will work.

    Split the 'x' term up (put the -10x first since you can factorise it with the 2x^2 as you will see)

    2x^2-10x+3x-15
    =2x(x-5)+3(x-5)
    =(2x+3)(x-5)
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    Hint: -30 = 3 \times -10

    Edit: bleh, ignore this - listen to notnek.
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    (Original post by junayd1998)
    http://prntscr.com/b0ol03

    The numerator I can do but I can't do the denominator when they add the 2 to the x^2 i get confused and have no idea how to do it. Can anyone explain to me how to do.

    Thanks
    The previous posters are using the 'ac' method. Ignore that for now if you've never used it before.


    Your bracket look okay so far.

    So you need two numbers that multiply to give -15. There aren't too many combinations. Try some numbers then expand the brackets to check they work.

    If you're stuck, tell us what you've tried.
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    2x^2 - 7x - 15 = (2x + 3) (x -5)
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    (Original post by AdRiAnRsT)
    2x^2 - 7x - 15 = (2x + 3) (x -5)
    :sigh:
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    I usually just do the quadratic formula and times one of the results by two and see if it works when put back into the formula, if it doesn't then I times the other by two x)
 
 
 
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