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k in (-oo:+oo)
(2/5)*k+(4/7)*k+4/5 = 274/385 // - 274/385
(2/5)*k+(4/7)*k+4/5-(274/385) = 0
(2/5)*k+(4/7)*k+4/5-274/385 = 0
34/35*k+34/385 = 0 // - 34/385
34/35*k = -34/385 // : 34/35
k = -34/385/34/35
k = -1/11
k = -1/11
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