7.原式= (2x-2x-4y+x²-4y²)/(x²-4y²)
= (-4y+x²-4y²)/(x²-4y²)
8.原式=[ (x+3)²-(x+2)² ]/ [(x+2)(x-2)(x+3) ] × (2-x)/(2x+5)
=(2x+5)/ [(x+2)(x-2)(x+3) ] × (2-x)/(2x+5)
= -1/ [(x+2)(x+3) ]
= -1(x²+5x+6)
9.原式=(x+1+x²-1-x+1)/(x²-1) × (x²-1)/x³
= (x²+1)/x³
10.原式=(x-1)³/x³ × x²/(x²-1)²
=(x-1)³x²/x³(x+1)²(x-1)²
=(x-1)/x(x+1)²
11.原式=[3x³(2x-1)-4x³+2x²]/[ (x+1)(2x-1)] × (x+1)/x²
=(6x²-7x+2)/(2x-1)
=(2x-1)(3x-2)/(2x-1)
=3x-2