<span> (2х+1)²-(2х+3)(2х-3)=0
4х²+4х+1-4х²+9=0
4х=-10
х=-2,5
</span>
Вот..............................................................................
10m2(-5m2-1)(-m-6)
20m(-10m-1)(-m-6)
(-200m^2-20m)(-m-6)
200m^3+1200m^2+20m^2+120m
200m^3+1220m^2+120m
А)=(2х^2-4х^3)+(1-7х)
б)=(7а^4-2а^3+5а)-(8а+9)