Question

нужно.Или скажите если есть готовые ответы​

Answer 1

Объяснение:

$1)x + y = 120 \\ {x}^{2} + {y}^{2} = 10400 \\ \\ x = 120 - y \\ {(120 - y)}^{2} + {y}^{2} = 10400 \\ \\ x = 120 - y \\ 14400 - 240y + {y}^{2} + {y}^{2} = 10400 \\ \\ x = 120 - y \\ 2 {y}^{2} - 240y + 4000 = 0 \\ \\ x = 120 - y \\ {y}^{2} - 120y + 2000 = 0 \\ \\ y1 = 100 \\ x1 = 20 \\ \\ y2 = 20 \\ x2 = 100$

$2) \frac{5}{x} - \frac{2}{y} = 11 \\ \frac{3}{x} + \frac{4}{y} = 17 \\ \\ 5y - 2x = 11xy \\ 3y + 4x = 17xy \\ \\ 10y - 4x = 22xy \\ 3y + 4x = 17xy \\ \\ 13y = 39xy \ \\ \ 39x = 13 \\ \\ x = \frac{13}{39} \\ 3y + 4 \times \frac{13}{39} = 17y \times \frac{13}{39} \\ \\ x = \frac{13}{39} \\ 117y + 52 = 221y \\ \\ x = \frac{13}{39} \\ 104y = 52 \\ \\ x = \frac{13}{39} \\ y = 0.5$

$3)xy = 80 \\ \frac{x + y}{x - y} = \frac{3}{2} \\ \\ x = \frac{80}{y} \\ \frac{ \frac{80}{y} + y }{ \frac{80}{y} - y } = \frac{3}{2} \\ \\ x = \frac{80}{y} \\ \frac{80 + {y}^{2} }{y} \div \frac{80 - {y}^{2} }{y} = \frac{3}{2} \\ \\ x = \frac{80}{y} \\ \frac{80 + {y}^{2} }{80 - {y}^{2} } = \frac{3}{2} \\ \\ x = \frac{80}{y} \\ 160 + 2 {y}^{2} = 240 - 3 {y}^{2} \\ \\ x = \frac{80}{y} \\ 5 {y}^{2} = 80 \\ \\ x = \frac{80}{y} \\ {y}^{2} = 16 \\ \\ x = \frac{80}{4} \\ y = 4 \\ \\ x = 20 \\ y = 4$