ПОМОГИТЕ СРОЧНО С АЛГЕБРОЙ

$\frac{7 {z}^{3} }{ {y}^{4} } = 7 {x}^{0} {y}^{ - 4} {z}^{3}$

ответ: б

$( \sqrt{6} )^{ - 4} + {( \frac{6}{ \sqrt{2} } )}^{ - 2} \times ( \frac{1}{2} ) ^{ - 3} = \\ = \frac{1}{( \sqrt{6})^{4} } + ( \frac{ \sqrt{2} }{6} ) ^{2} \times {2}^{3} = \\ = \frac{1}{36} + \frac{2}{36} \times 8 = \\ = \frac{1}{36} + \frac{16}{36} = \frac{17}{36}$

ответ: в

$( {m}^{ - 2} + {n}^{ - 2}) \div ( {m}^{2} + {n}^{2} ) = \\ = ( \frac{1}{ {m}^{2} } + \frac{1}{ {n}^{2} } ) \ \times \frac{1}{ {m}^{2} + {n}^{2} } = \\ = \frac{ {n}^{2} + {m}^{2} }{ {m}^{2} {n}^{2} } \times \frac{1}{ {m}^{2} + {n}^{2} } = \frac{1}{ {m}^{2} {n}^{2} }$

ответ: а