=====c)9=====
[tex] \sqrt{75} = \sqrt{ {5}^{2} \times 3 } = 5 \sqrt{3} \\ 5 \sqrt{12} =5 \sqrt{ {2}^{2} \times 3 } = 5 \times 2 \sqrt{3} = 10 \sqrt{3} \\ 2 \sqrt{27} = 2\sqrt{ {3}^{2} \times 3 } = 2 \times 3 \sqrt{3} = 6 \sqrt{3} \\ a = 5 \sqrt{12} - 2 \sqrt{27} - \sqrt{75} \\ a = 10 \sqrt{3} - 6 \sqrt{3} - 5 \sqrt{3} \\ a = - 1\sqrt{3} \\ a {}^{4} = ( - \sqrt{3} ) {}^{4} = { \sqrt{3} }^{4} \\ {a}^{4} = \sqrt{3} {}^{2} \times \sqrt{3} {}^{2} = 3 \times 3 = 9[/tex]
minus la putere para da plus
