Question

a1+a5=24 a1*a3=60
нужно найти a1 и d прогрессия​

Answer 1

Ответ:

$a1 = 5 \\ d = 3.5$

Объяснение:

$a1 + a5 = 24 \\ a1 \times a3 = 60 \\ a1 = x \\ x + x + 4d = 24\\ 2x + 4d = 24 \\ x + 2d = 12 \\ x = 12 - 2d \\ {(12 - 2d)}^{2} + 24d - 4{d}^{2} = 60 \\ 144 - 48d + 4 {d}^{2} + 24d - 4 {d}^{2} - 60 = 0 \\ 24d = 84 \\ d = 3.5 \\ x = 12 - 7 = 5 \\ a1 = 5$