ivan35567 №714
б)x²y-y+xy²-x = (x²y + xy²) - (x+y) = xy * (x+y) - (x+y) = 
= (xy - 1)(x+y)
x=4
y=0,25
(xy - 1)(x+y) = (1 - 1)(4,25) = 
=0 * 4,25 = 0
№713
б)3x³ - 2y³- 6x²y² + xy = (3x³ + xy) - (6x²y² + 2y³) = 
=x * (3x² + y) - 2y² * (3x² + y) = 
= (x - 2y²) (3x²+y) 
при x = 2/3  и  y=1/2
(x - 2y²) (3x²+y) = (2/3 - 2 * 1/4) (3 * 4/9 - 1/2)=
=(2/3 - 1/2)(4/3 + 1/2) = 1/6 * 11/6 = 11/36
№715
а)ax-y+x-ay=(ax-ay) + (x-y) = a * (x-y) + (x-y) = (a+1)(x-y)
б)ax-2by+ay-2bx=(ay-2by) + (ax-2bx) - y * (a-2b) + x * (a-2b) = (x+y)(a-2b)