1)
3(x-1)(2x+3)
3(2x²-2x+3x-3)
3(2x²+x-3)
6x²+3x-9
2)
(x+5)(x-3)= (x+1)²-16
x²+5x-3x-15=x²+x+x+1-16
x²-2x-15= x²+2x-15
3)
(a+b/2)²+3b²/4
(a+b/2)(a+b/2)+3b²/4
a²+ab/2+ab/2+3b²/4
a²+2ab++3b²/4⇔(a+b/2)²+3b²/4
4)
(x-2)(x+3)(x-1)=x³-7x+6
(x²-2x+3x-6)(x-1)
(x²+x-6)(x-1)
x³+x²-6x-x²-x+6
x³-7x+6
