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Math Help - Urgent help needed parallelogram

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    Urgent help needed parallelogram

    In parallelogram ABCD, angle A is x(x+1) and angle B is 108. Show your work in finding the value of x
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    Quote Originally Posted by OneidaFL View Post
    In parallelogram ABCD, angle A is x(x+1) and angle B is 108. Show your work in finding the value of x
    \angle{A} = \angle{C} and \angle{B} = \angle{D}.

    Also, the angle sum of a parallelogram is 360^{\circ}.


    Therefore:

    \angle{A} + \angle{B} + \angle{C} + \angle{D} = 360^{\circ}

    x(x + 1) + 108 + x(x + 1) + 108 = 360

    2x(x + 1) + 216 = 360

    2x(x + 1) = 144

    2x^2 + 2x = 144

    2x^2 + 2x - 144 = 0

    x^2 + x - 72 = 0

    (x + 9)(x - 8) = 0

    x + 9 = 0 or x - 8 = 0

    x = -9 or x = 8.


    Since you can't have a negative angle in a parallelogram, that means x = 8.
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