Sn = (b1*(1- q^n))/(1 - q) ==>
S5 = (4*(1- 2^5))/(1 - 2) = 124
Y-5=3x
2y+x=-4
y=3x+5
2(3x+5)+x=-4
2(3x+5)+x=-4
6x+10+x=-4
7x=-14
x=-2
y=3x+5
y=3*(-2)+5=-6+5=-1
<span>Ответ: (-2;-1)</span>
а) (а-3)*(а+3)
б) (а+2)(а^2-2a+4)
в)(1-b)(1+b+b^2)
г)(х+5)^2
д)(3a-1)^2
е)3a^2(5a - b)
ж)y(y^2-49)=y(y-7)(y+7)
з)x(y+z)+3(y+z) = (x+3)*(y+z)