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Question-132597




Question Number 132597 by Study last updated on 15/Feb/21
Commented by mr W last updated on 15/Feb/21
((156)/(x+7))=((156)/x)−14  156x=156(x+7)−14x(x+7)  x^2 +7x−78=0  (x−6)(x+13)=0  x=6, −13 (rejected)  he expected to do the job in 6 hours.
$$\frac{\mathrm{156}}{{x}+\mathrm{7}}=\frac{\mathrm{156}}{{x}}−\mathrm{14} \\ $$$$\mathrm{156}{x}=\mathrm{156}\left({x}+\mathrm{7}\right)−\mathrm{14}{x}\left({x}+\mathrm{7}\right) \\ $$$${x}^{\mathrm{2}} +\mathrm{7}{x}−\mathrm{78}=\mathrm{0} \\ $$$$\left({x}−\mathrm{6}\right)\left({x}+\mathrm{13}\right)=\mathrm{0} \\ $$$${x}=\mathrm{6},\:−\mathrm{13}\:\left({rejected}\right) \\ $$$${he}\:{expected}\:{to}\:{do}\:{the}\:{job}\:{in}\:\mathrm{6}\:{hours}. \\ $$

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