А)7/14=1/2=0.5
б)при х=-0.5
-х+1=х+2
х+х=1-2
2х=-1
х=-0.5
в)хз
А1+9d=4
2a1+18d
S19 = ------------- • 19 = (a1+9d)•19 =
2
= 4•19 = 76
<span>а) 25x-x^3=x(25-x²)=x(5-x)(5+x)
б) 2x^2-20x+50=</span>2(x²-10x+25)=2(x-5)²
1) 9+2(2х+1)=1
9+4х+2=1
4х= -10
х= -2,5
2) 4+3(10х+7)= -5
4+30+21= -5
30х= -30
х= -1
3) 4+5(-3х+7)= -9
4-15х+35= -9
-15х=-48
х=3,2