1) (5x+y)²-(x-2y)²=25x²+10xy+y²-x²+4xy-4y²=24x²+14xy-3y².
2) (3x-2)(3x+2)-(1-x)(1+x)=9x²-4-1+x²=10x²-5=5*(2x-1).
3) 6a-(4a-3)²=6a-16a²+24a-9=-16a²+30a-9.
4)(x-5)²=5x²-(2x-1)(2x+1)
x²-10x+25=5x²-4x²+1
x²-10x+25=x²+1
10x=24
x=2,4.
5) (7x-3)(2x-5)-2*(4x-3)²=14x²-41x+15-32x²+48x-18=-18x²+7x-3.
6) (x²+x+1)(x-1)-0,5*(2x-1)(2x+1)=(x-1)(x²+x+1)-0,5*(4x²-1)=
=x³-1-2x²+0,5=x³-2x²-0,5=(-0,5)³-2*(-0,5)²-0,5=-0,125-0,5-0,5=-1,125.