1)(-7x+2y)²-14x(3x-2y)=49x²-28xy+4y²-42x²+28xy=7x²+4y²
2)(-5x-y)²-10x(-7+y)=25x²+10xy+y²+70x-10xy=25x²+y²+70x
3)(-8x+5y)²-16x(-8x-5y)=64x²-80xy+25y²+128x²+80xy=172x²+25y²
4)y(7y+4x)-(2x+y)²=7y²+4xy-4x²-4xy-y²=6y²-4x²
5)y(-7y+6x)-(-3x-y)²=-7y²+6xy-9x²-6xy-y²=-8y²-9x²