Объяснение:
(x² + 6x)² - 4(x² + 6x + 1) - 17 = 0
t = (x² + 6x)
t² - 4(t + 1) - 17 = 0
t² - 4t - 4 - 17 = 0
t² - 4t - 21 = 0
t² + 3t - 7t - 4 - 17 = 0 (Теорема Виета)
t² + 3t - 7t - 21 = 0
t(t + 3) - 7(t + 3) = 0
(t + 3)(t - 7) = 0
t₁ = -3; t₂ = 7
x² + 6x + 3= 0 x² + 6x - 7 = 0
D = b² - 4ac D = b² - 4ac
D = 6² - 4 * 1 * 3 D = 6² - 4 * 1 * (-7)
D = 36 - 12 D = 36 + 28
D = 24 D = 64
Диалог 1.
Jim: Here`s my present. I hope you like it.
Billy: That`s very kind of you! I`v always wanted cap like this!
Jim: I`m glad you like this. Try it on and see if it fits.
Billy: I think this is coll. What do you think?
Jim: It matches the colour of your T-shirt. I`m glad you liked it.
Диалог 2.
Jim: This is for you.
Shelley: That`s very kind of you! What is it?
Jim: Open it and see.
Shelley: Wow. It`s a lovely skirt.
Jim: I`m glad you like this. Are they your size?
Shelley: Oh, no. They're too big.
Jim: That`s all right. You can exchange them.
Shelley: Thanks
Jim: Don`t mention it.
Вроде так, если каждый диалог нужна была новая вещь. Если я не правильно поняло, то можно просто слово поменять.
6×2=12
12 насосов за 5 часов
3 насоса за 15ч