#1.8b³-3b³+17b+3b³-8b+6=8b³+9b+6

#2.a)(2x-4y+5)-(x+4y+5)=2x-4y+5-x-4y-5=x-8y
б)2a^7(a²-5)+9a^7=2a^9-10a^7+9a^7=2a^9-a^7
в)7x(y²+xz)=7xy²+7x²z

#3. a)2(2x-7)-3(x+2)=6
4x-14-3x-6=6
x-20=6
x=6+20
x=26

б)10x-5=2(8x+3)-5x
10x-5=16x+6-5x
16x-10x-5x=-5-6
x=-11

#4.(2m²n+3n)(2m²-3)=4m^4×n-6m²n+6m²n-9n=4m^4×n - 9n

#5.
6a(a-x+c)+6x(a+x-c)-6c(a-x-c)=6a²-6ax+6ac+6ax+6x²-6cx-6ac+6cx-6c²=
=6a² +6x²-6ac+6cx-6c²