Упростите выражение: 3с+а/4с-а-7с/4с 2р/р+3+3-р/р+3 х^2/х-4+4х/4-х m/m^2-n^2-n/m^2-n^2

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$\frac{3c + a}{4c} - \frac{a - 7c}{4c} = \frac{3c + a - a + 7c}{4c} = \frac{10c}{4c} = \frac{5}{2} = 2 \frac{1}{2} = 2.5$
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$\frac{2p}{p + 3} + \frac{3 - p}{p + 3} = \frac{2p + 3 - p}{p + 3} = \frac{p + 3}{p + 3} = 1$
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$\frac{ {x}^{2} }{x - 4} + \frac{4x}{4 - x} = \frac{ {x}^{2} }{x - 4} - \frac{4x}{x - 4} = \frac{ {x }^{2} - 4x}{x - 4} = \frac{x(x - 4)}{x - 4} = x$
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$\frac{m}{ {m}^{2} { - n}^{2} } - \frac{n}{m ^{2} - {n}^{2} } = \frac{m - n}{ { {m}^{2} - n}^{2} } = \frac{m - n}{(m - n)(m + n)} = \frac{1}{m + n}$