Question

помогите пожалуйста, дам 40 балов​

Answer 1

$1.$

$11 {x}^{2} = 99 \\ {x}^{2} = 9 \\ x =±3$

${5x}^{2} - 45x = 0 \\ 5x(x - 9) = 0 \\ 5x = 0 \: \: \: \: \: x = 0 \\ x - 9 = 0 \: \: \: \: \: x = 9$

${9x}^{2} - 81 = 0 \\ {9x}^{2} = 81 \\ {x}^{2} = 9 \\ x = ±3$

${3x}^{2} + 27 = 0 \\ {3x}^{2} = - 27 \\ {x}^{2} = - 9 \\ x = ∅$

${ - 13x}^{2} = 0 \\ {x}^{2} = 0 \\ x = 0$

$2.$

${5x}^{2} - 7x + 2 = 0 \\ D = {( - 7)}^{2} - 4 \times 5 \times 2 = 49 - 40 = 9 \\ x1x2 = \frac{ - ( - 7)± \sqrt{9} }{2 \times 5} = \frac{7±3}{10} \\ x1x2 = 0.4 \: ; \: 1$

$5(1 - {x}^{2} ) = 6(3 - {x}^{2} ) - 13 \\ 5 - {5x}^{2} = 18 - {6x}^{2} - 13 \\ - {5x}^{2} + {6x}^{2} + 5 - 18 + 13 = 0 \\ {x}^{2} = 0 \\ x = 0$

$12(x - 8) = {(x + 8)}^{2} \\ 12x - 96 = {x}^{2} + 16x + 64 \\ {x}^{2} + 16x + 64 - 12x + 9 6= 0 \\ {x}^{2} + 4x + 160 = 0 \\ D = { 4}^{2} - 4 \times 1 \times 160 = 16 - 640 = - 626 \\ x = ∅$

Только 2 смог