Question

можете решить пожалуйста СРОЧНО!!!
е) или д) или в)

Answer 1

е)
$9x {}^{2} - 20x - 21 = 0 \\ d = 20 {}^{2} + 4 \times 9 \times 21 = 400 + 756 = 1156 \\ \sqrt{1156} = 34 \\ x1 = \frac{20 - 34}{18} = \frac{ - 14}{18} = \frac{ - 7}{9} \\ x2 = \frac{20 + 34}{18} = \frac{54}{18} = 3 \\ 25x {}^{2} + 10x - 4 = 0 \\ d = 10 {}^{2} + 4 \times 4 \times 25 = 100 + 400 = 500 \\ x1 = \frac{ - 10 - 10 \sqrt{5} }{50 } = - \frac{ 1 + \sqrt{5} }{5} \\ x2 = \frac{ - 10 + 10 \sqrt{5} }{50} = \frac{ - 1 + \sqrt{5} }{5} \\ - 5x {}^{2} + 6x - 1 = 0 \\ d = 6 {}^{2} - 4 \times 5 = 36 - 20 = 16 \\ \sqrt{16} = 4 \\ x1 = \frac{ - 6 - 4}{ - 10} = \frac{ - 10}{ - 10} = 1 \\ x2 = \frac{ - 6 + 4}{ - 10} = \frac{ - 2}{ - 10} = \frac{1}{5}$