4,8d^3+6,4d^2-2,4d
d(4,8d^2+6,4d)
При вычитании показатели степеней делятся, т. е. 2х-5х=-3х
Sn = b1/(1 - q)
Sn = 12/(1 - 1/3) = 12*(2/3) = 8
2X^2 + 3 = 3 - 7X
2X^2 + 3 - 3 + 7X = 0
2X^2 + 7X = 0
2X * ( X + 3,5 ) = 0
--------------------
2X = 0
X = 0
------------------
X + 3,5 = 0
X = - 3,5
-----------------
Ответ 0 ; - 3,5
===================
5X - 4Y = 12
X - 5Y = - 6
----------------
X = 5Y - 6
5*( 5Y - 6) - 4Y = 12
25Y - 30 - 4Y =12
21Y = 42
Y = 2
X = 10 - 6 = 4
----------
Ответ X = 4 ; Y = 2