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m in (-oo:+oo)
-(4*m)-9 = 4*m-105 // - 4*m-105
105-(4*m)-(4*m)-9 = 0
105-4*m-4*m-9 = 0
96-8*m = 0 // - 96
-8*m = -96 // : -8
m = -96/(-8)
m = 12
m = 12
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