2(а+3)(а-3)=2(а²-9)=2а²-18
а(х-у)+5(х+у)=5а(х²-у²)=5ах²-5ау²
3(x-4)=5(3-x)
3x-12=15-5x
3x+5x=15+12
8x=27
x=27/8
x=3 3/8
x=3,375
1) (3b(-a9-3b))*(3b+(a-3b))=(3b-a+3b)*(3b+a-3b)=(6b-a)*(3b+a-3b)=(6b-a)*a=a*(6b-a)
2) 25-10y+y^2+y^2-7y=25-17y+2y^2=2y^2-17y+25