1.выполните действия:
а) (a2 – 2b)2
б) (–7x – 1)2
в) (–5a +2b4)2
г) (x–12)(x+ 12)
д) (– 4n3 +7)(4n3+7)
е) (3x –y) 2
ж) (– 6n – 2)2
з) (– 7c + 8x3)2
и) (b – 13a)(13a +b)
к) (–5m4+ 3)(3 +5m4)
а) (2a +3)(a –3) – 2a(4 – 6a)
б) (2x + 3)(3 –2x) – (2x –5)2 –10x
Вот накалякал. Разбирайся :)
xy/(x+y) = 5
xz/(x+z) = 7
yz/(y+z) = 9
xy = 5x + 5y
xz = 7x + 7z
yz = 9y + 9z
x(y-5) = 5y
x = 5y/(y-5)
5yz/(y-5) = 35y/(y-5) + 7z
5yz = 35y + 7z * (y-5)
5yz = 35y + 7yz - 35z
2yz + 35y = 35z
y(2z + 35) = 35z
y = 35z/(2z + 35) = z/(2z/35 + 1)
35z^2/(2z + 35) = 315z/(2z + 35) + 9z
35z^2 = 315z + 9z*(2z + 35)
35z^2 = 315z + 18z^2 + 315z
17z^2 = 630z
z=630/17
y = 35*630/(2*630/17 + 35)/17 = 35*630/(1260 + 595) = 22050/1855 = 630 / 53
x = 5*630/(630/53 - 5)/53 = 5*630/((630/53 - 5)*53) = 5*630/365 = 630/73