Question

Решите пожалуйста объведённые номера.

Answer 1

Ответ:

$1) \ 10x{}^{2} - 20x = 0 ( \div 10) \\ x {}^{2} - 2x = 0 \\ x(x - 2) = 0 \\ x = 0 \\ or \\ x - 2 = 0 \\ x = 2.$

$2) \ 5x {}^{2} = 15x \\ 5x {}^{2} - 15x = 0( \div 5) \\ x {}^{2} - 3x = 0 \\ x(x - 3) = 0 \\ x = 0 \\ or \\ x - 3 = 0 \\ x = 3.$

$3) \ 6x {}^{2} - 7x - 3 = 0 \\ D = ( - 7) {}^{2} - 4 \times 6 \times ( - 3) = 49 + 72 = 121 \\ x = \dfrac{ - ( - 7) - 11}{2 \times 6} = \dfrac{7 - 11}{12} = \dfrac{ - 4}{12} = - \dfrac{1}{3} \\ x = \dfrac{7 + 11}{12} = \dfrac{18}{12} = \dfrac{3}{2} = 1.5.$