(4p -q)/12p²q +(p -5q)/15pq² =(5q(4p-q) +4p(p-5q)) /60p²q² =
(20pq -5q² +4p² -20pq)/60p²q² =(4p² -5q²)/60p²q² или 1/15q² -1/12p².
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x² -x +1 -x³/(x+1) = ((x+1)(x² -x +1) -x³)/(x+1) = (x³ +1³ -x³)/(x+1) = 1/(x+1).
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(m -3n)/8n(m+n) - (m+3n)/8n(m-n) = ((m-3n)(m-n) -(m+3n)(m+n)) /8n(m+n)(m-n) =
(m² -4mn +3n²- m² -4mn -3n²)/ 8n(m+n)(m-n) = -8mn/ 8n(m+n)(m-n) =
m/(n+m)(n-m).
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