Ya Allah udh nanya 4 kali gk ada yg jawab, emng soalnya susah banget apa? jawab ya klo ada yg tau pliisss, soalnya buat nanti

[tex] |a + 2b| = \sqrt{ |a| {}^{2} + { |2b| }^{2} + 2 |a| |2b|cos \alpha } \\ \\ |a + 2b| = \sqrt{64 + 64 + 2(8)(8)( - \frac{7}{16} )} \\ \\ |a + b| = \sqrt{128 + 128 \times ( - \frac{7}{16}) } \\ \\ |a + b| = \sqrt{128 - 56} \\ \\ |a + b| = \sqrt{72} = 6 \sqrt{2} [/tex]