SOLUTION: please help me solve this equation : {{{ x/2 > 5/(x+4) +4 }}}

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Question 263390: please help me solve this equation :
+x%2F2+%3E+5%2F%28x%2B4%29+%2B4+

Found 3 solutions by CubeyThePenguin, josgarithmetic, ikleyn:
Answer by CubeyThePenguin(3113) About Me  (Show Source):
You can put this solution on YOUR website!
Multiply both sides by 2(x+4).

x(x+4) > 5(2) + 4(2)(x+4)
x^2 + 4x > 10 + 8x + 32
x^2 - 4x - 42 > 0

The solution is the area outside the quadratic's roots.

Answer by josgarithmetic(39618) About Me  (Show Source):
Answer by ikleyn(52793) About Me  (Show Source):
You can put this solution on YOUR website!
please help me solve this equation :
+x%2F2 > 5%2F%28x%2B4%29 + 4
~~~~~~~~~~~~~

            The "solutions" from both @CubeyThePenguin and @josgaritmetic are WRONG.

            Below I brought the correct solution.


Rewrite it equivalently in this form


    x%2F2 - 5%2F%28x%2B4%29 - 4 > 0

    x - 10%2F%28x%2B4%29 - 8 > 0

    x%2A%28%28x%2B4%29%2F%28x%2B4%29%29 - 10%2F%28x%2B4%29 - 8%2A%28%28x%2B4%29%2F%28x%2B4%29%29 > 0    <<<--- now we have common denominator (x+4)

    %28x%2A%28x%2B4%29+-+10+-+8%2A%28x%2B4%29%29%2F%28x%2B4%29 > 0

    %28x%5E2+%2B+4x+-+10+-+8x+-+32%29%2F%28x%2B4%29 > 0

    %28x%5E2+-+4x+-+42%29%2F%28x%2B4%29 > 0


The quadratic polynomial in the numerator has the roots


    x%5B1%2C2%5D = %284+%2B-+sqrt%284%5E2+%2B+4%2A42%29%29%2F2 = %284+%2B-+sqrt%28184%29%29%2F2 = 2+%2B-+sqrt%2846%29.


So, the numerator has the roots  x%5B1%5D = 2+-+sqrt%2846%29 = -4.782  and  x%5B2%5D = 2+%2B+sqrt%2846%29 = 8.782.


There are three critical points on the number line,  

    x%5B1%5D = 2+-+sqrt%2846%29 = -4.782,  -4  and  x%5B2%5D = 2+%2B+sqrt%2846%29 = 8.782.


They divide the number line in 4 intervals, from left to right

    (-oo,x%5B1%5D),  (x%5B1%5D,-4),  (-4,x%5B2%5D)  and  x%5B2%5D,oo).


The solution set for the given inequality is the union of the second and the fourth intervals.

Solved.