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Math Help - Quadratic formula questions

  1. #1
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    Unhappy Quadratic formula questions

    Can someone help me solve these questions i'm finding it really difficult.....

    SIMULTANEOUS EQUATION

    2x+y=7
    3x-y=3

    SOLVE ALGEBRAICALLY

    (a) y= x^2 + 3x -8
    y= x - 5

    (b) Write down the formula to find the roots of the equation
    (c) Use the formula to find the roots of: 3x^2-9x-16=0
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  2. #2
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    Quote Originally Posted by GAVREED2 View Post

    2x+y=7
    3x-y=3

    2x+y=7 ...(1)
    3x-y=3 ...(2)

    Using (1) 2x+y=7\implies y = 7-2x and subbing this into (2)

    3x-(7-2x)=3 Can you finish it?


    Quote Originally Posted by GAVREED2 View Post
    .....



    SOLVE ALGEBRAICALLY

    (a) y= x^2 + 3x -8
    y= x - 5
    y=y

    x^2 + 3x -8=x-5

    x^2 + 2x -3= 0

    Can you have a go from here? (if not my answer to the next question might help!)


    Quote Originally Posted by GAVREED2 View Post
    (c) Use the formula to find the roots of: 3x^2-9x-16=0
    For ax^2+bx+c=0\implies x = \frac{-b\pm\sqrt{b^2-4ac}}{2a}
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