3.
.....=(х+7)(4а²+3)
при а= -0,5, х=1,05
(1,05+7)(4*(-0,5)² +3)=8,05*4=32,2
4.
15a² b +10a³b²c=5a²b(3+2abc)
3(m+n)-(m+n)²=(m+n)(3-m-n)
6x(x-1) -(1-x)²= -6x(1-x) - (1-x)²= (1-x)( -6x -1-x)=(1-x)(-7x-1)
2ay -b+by -2a=2a(y-1) -b(1-y)=2a(y-1) +b(y-1)=(y-1)(2a+b)