1)2x (x+2)-3=9x 2)x(в квадрате)=11x-18 3)(x+4)(в квадрате)+(x-4)(в квадрате)...

Ответ:

$1)2 {x}^{2} + 4x - 3 - 9x = 0 \\ 2 {x}^{2} - 5x - 3 = 0 \\ d = 25 + 24 = 49 = {7}^{2}$

$x1 = \frac{5 + 7}{4} = \frac{12}{4} = 3 \\ x2 = \frac{5 - 7}{2} = - \frac{2}{2} = - 1$

$2) {x}^{2} - 11x + 18 = 0 \\ d = 121 - 72 = 49 = {7}^{2} \\ x1 = \frac{11 + 7}{2} = \frac{18}{2} = 9$

$x2 = \frac{11 - 7}{2} = \frac{4}{2} = 2$

$3)(x + 4) {}^{2} + (x - 4) {}^{2} = 36 \\ {x}^{2} + 8x + 16 + {x}^{2} - 8x + 16 = 36 \\ 2 {x}^{2} + 32 = 36 \\ 2 {x}^{2} = 36 - 32$

$2 {x}^{2} = 4 \\ {x}^{2} = 4 \div 2 \\ {x}^{2} = 2 \\ x1 = \sqrt{2} \\ x2 = - \sqrt{2}$