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D( x )
x = 0
x = 0
x = 0
x in (-oo:0) U (0:+oo)
9/8 = 144/x // - 144/x
9/8-(144/x) = 0
9/8-144*x^-1 = 0
-144*x^-1 = -9/8 // : -144
x^-1 = 1/128
-1 < 0
1/(x^1) = 1/128 // * x^1
1 = 1/128*x^1 // : 1/128
128 = x^1
x = 128
x = 128
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