28.
1) a(b-2)/5(b-2)=a/5( b-2 сокращаем сверху и снизу)
2)3(x+4)/c(x+4)=3/c
3)ab(y+3)/a^2b(y+3)=ab/a^2b=1/a
4)15a(a-b)/20b(a-b)=15a/20b=3a/ 4b
29.
1)3a+12b/6ab=3(a+4b)/6ab=a+4b/ 2ab
3)2a-4/3(a-2)=2(a-2)/3(a-2)=2/3
5)a-3b/a^2-3ab=a-3b/a(a-3b)=1/ a
2)15b-20c/10b=5(3b-4c)/10b=3b-4c/ 2b
4)5x(y+2)/6y+12=5x(y+2)/6(y+2)=5x/ 6
6)3x^2+15xy/x+5y=3x(x+5y)/x+5y=3x
30.
1)y^2-16/3y+12=(y-4)(y+4)/3(y+4)=y-4/ 3
2)5x-15y/x^2-9y^2=5(x-3y)/(x-3y)(x+3y)=5/ x+3y
3)(c+2)^2/7c^2+14c=(c+2)^2/7c(c+2)=c+2/ 7c
4)6cd-18c/(d-3)^2=6c(d-3)/(d-3)^2=6c/ d-3
5)a^2+10a+25/a^2-25=(a+5)^2/(a-5)(a+5)==a+5/ a-5
6)y^2-9/y^2-6y+9=(y-3)(y+3)/(y-3)^2=y+3/ y-3
(/-дробь)
4xy+9=21y, 18=17y-3xy ; 4xy=21y-9 , xy= (21y-9)/4 ; 18= 17y-3((21y-9)/4 ; отсюда у= 9 ; а ху =45
B+b+a+a=2b+2a
x-y-z+y=y+y+x-z=2y+x-z
c-10+15-c=c-c10+15=25
x+x-15+15=2x-30
m+m+1+m-20=3m-19
(3 a - 5 b) (a^2 + 2 a b - 4 b^2) - (3 a - 5 b) (a^2 + 2 a b - 7 b^2)
3 a^3 + a^2 b - 22 a b^2 + 20 b^3 - (3 a - 5 b) (a^2 + 2 a b - 7 b^2)
3 a^3 + a^2 b - 22 a b^2 + 20 b^3 - 3 a^3 + a^2 b - 31 a b^2 + 35 b^3
3 a^3 + a^2 b - 22 a b^2 + 20 b^3 + -3 a^3 - a^2 b + 31 a b^2 - 35 b^3
(20 b^3 - 35 b^3) + (31 a b^2 - 22 a b^2) + (a^2 b - a^2 b) + (3 a^3 - 3 a^3)
-15 b^3 + (31 a b^2 - 22 a b^2) + (a^2 b - a^2 b) + (3 a^3 - 3 a^3)
-15 b^3 + 9 a b^2 + (a^2 b - a^2 b) + (3 a^3 - 3 a^3)
-15 b^3 + 9 a b^2 + (3 a^3 - 3 a^3)
9 a b^2 - 15 b^3
<span>3 b^2 (3 a - 5 b)</span>