Explicație pas cu pas:
[tex]a = (3 \sqrt{8} - 9 \sqrt{32} - 3 \sqrt{128} ) \div ( - 3 \sqrt{2}) \\ = (3 \sqrt{ {2}^{3} } - 9 \sqrt{ {2}^{5} } - 3 \sqrt{ {2}^{7} }) \div ( - 3 \sqrt{2} ) \\ = (3 \times 2 \sqrt{2} - 9 \times {2}^{2} \sqrt{2} - 3 \times {2}^{3} \sqrt{2}) \div ( - 3 \sqrt{2}) \\ = (6 \sqrt{2} - 36 \sqrt{2} - 24 \sqrt{2}) \div ( - 3 \sqrt{2}) \\ = ( - 54 \sqrt{2} \div ( - 3 \sqrt{2}) \\= 54 \div 3 = 18 [/tex]
[tex]b = ( \frac{3}{2 \sqrt{3} } - \frac{15}{ \sqrt{27} } ) \div \frac{21}{ \sqrt{48} } \\ = ( \frac{3}{2 \sqrt{3} } - \frac{15}{ \sqrt{{3}^{3}} } ) \div \frac{21}{ \sqrt{ {2}^{4} \times 3} } \\ = ( \frac{3}{2 \sqrt{3} } - \frac{15}{3 \sqrt{3} }) \div \frac{21}{ {2}^{2} \sqrt{3}} \\ = ( \frac{3}{2 \sqrt{3} } - \frac{5}{ \sqrt{3} }) \div \frac{21}{4 \sqrt{3}} \\ = ( \frac{3}{2 \sqrt{3} } - \frac{10}{2 \sqrt{3} }) \times \frac{4 \sqrt{3} }{21} \\ = - \frac{7}{2 \sqrt{3} } \times \frac{4 \sqrt{3} }{21} = - \frac{2}{3} [/tex]
