Объяснение:
3.
(2x+3y)²-(2x-3y)²=(2x+3y+2x-3y)*(2x+3y-2x+3y)=4x*6y=24xy.
4.
x³+2x²-x-2=0
x²*(x+2)-(x+2)=0
(x+2)*(x²-1)0
(x+2)*(x+1)*(x-1)=0
x₁=-2 x₂=-1 x₃=1.
5.
57³-31³=(57-31)*(57²+57*31+31²)=26*(57²+57*31+31²)=2*13*(57²+57*31+31²).
