Question

Решить 2 легких уравнения!

Answer 1

Ответ:

$1) \: \: (1.8 - 0.3y)(2y + 9) = 0 \\ 3.6y + 16.2 - 0.6 {y}^{2} - 2.7y = 0 \\ 0.9y + 16.2 - 0.6 {y}^{2} = 0 \\ - 0.6 {y}^{2} + 0.9y + 16.2 = 0 \\ 0.6 {y}^{2} - 0.9y - 16.2 = 0 \\ 6 {y}^{2} - 9y - 162 = 0 \\ d = ( - 9 {)}^{2} - 4 \times 6 \times ( - 162) =81 + 3888 = 3969 \\ y = \frac{9 + \sqrt{3969} }{2 \times 6} = \frac{9 + 63}{12} = \frac{72}{12} = 6 \\ y = \frac{9 - \sqrt{3969} }{2 \times 6} = \frac{9 - 63}{12} = - \frac{54}{12} = - 4.5 \\ \\ 2) \: \: (5y + 4)(1.1y - 3.3) = 0 \\ 5.5 {y}^{2} - 16.5y + 4.4y - 13.2 = 0 \\ 5.5 {y}^{2} - 12.1y - 13.2 = 0 \\ 55 {y}^{2} - 121y - 132 = 0 \\ d = ( - 121 {)}^{2} - 4 \times 55 \times ( - 132) = 14641 + 29040 = 43681 \\ y = \frac{121 + \sqrt{43681} }{2 \times 55} = \frac{121 + 209}{110} = \frac{330}{110} = 3 \\ y = \frac{121 - \sqrt{43681} }{2 \times 55} = \frac{121 - 209}{110} = - \frac{88}{110} = - \frac{8}{10} = 0.8$