Pre-calculus need help!!

posted by Isis

Quadratic Formula
1.) x+6/x=-7
2.) 4x/x+4 + 3/x-1 = 15/x^2+3x-4
3.) x+3/x - 2/x+3 = 6/x^2+3x

formula:
-B+ sqrt B^2 + (-4)(a)(c)/2a
f u only wanted to use the formula it's not necessary though.

please help me! it's going to pass tomorrow!! please!

  1. Reiny

    your formula should say:
    x = (-b ± √(b^2 - 4ac) )/(2a)

    1. x + 6/x = -7
    each term by x

    x^2 + 6 = -7x
    x^2 + 7x + 6 = 0
    it factors, no need for the formula
    (x+1)(x+6) = 0
    x = -1 or x = -6

    2. you probably meant:
    4x/(x+4) + 3/(x-1) = 15/(x^2 + 3x - 4)
    4x/(x+4) + 3/(x-1) = 15/((x-1)(x+4) )
    multiply each term by (x+4)(x-1) , the LCD
    4x(x-1) + 3(x+4) = 15
    4x^2 - 4 + 3x + 12 = 15
    4x^2 + 3x -7 = 0
    x = (-3 ±√(9-4(4)(-7)) )/8
    = (-3 ±√121)/8 = (-3 ± 11)/8
    x = 1 or x = -7/4

    or.... we could have factored it again
    (x-1)(4x + 7) = 0
    x = 1 or x = -7/4

    3. again, brackets will be essential.
    (x+3)/x - 2/(x+3) = 6/( x(x+3))
    the LCD is x(x+3) , so multiply each term by x(x+3)
    You can take it from there.

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