1) a1=5
a2=9
a3=13
a4=17
a5=21
5+9+13+17+21=65
2) a1=10
a2=12
a3=14
a4=16
a5=18
a6=20
a7=22
a8=24
a9=26
a10=28
a11=30
a12=32
a13=34
10+12+14+16+18+20+22+24+26+28+30+32+34=286
3) a1=-18
a2=-22
a3=-26
a4=-30
a5=-34
a6=-38
a7=-42
a8=-46
a9=-50
a10=-54
a11=-58
a12=-62
a13=66
18+22+26+30+34+38+42+46+50+54+58+60+66=-546
<span>5+2х + 3 =7х-2
5х-7х=-2-8
-2х=-10
х=5 </span>
3x+4y = 5. 3x+4y = 5
8x-2y = 4 -2y = 4-8x
3x+4(4x-2) = 5. 3x+16x-8 = 5
y = 4x-2. y = 4x-2
19x = 13. x = 13/19
y = 4x-2. y = 4*13/19 - 2
x = 13/19. x = 13/19
y = 52/19 - 2 y = 52/19-38/19
x = 13/19
y = 14/19