1)原式=[(99²-1)x99]÷98=[(99+1)(99-1)x99]÷98=9900
2)原式=2(1-2011²)/(2010x2012)=2[(1-2011)(1+2011)]/[(2011-1)(2011+1)]= -2
1)原式=[(4x²+25)(2x+5)(2x-5)]/[(4x²+25)(2x+5)]=2x-5
2)原式=[y(x+3)(x-3)]/[y(x+3)]=x-3
1)原式=[(m+2n)+(2m-n)][(m+2n)-(2m-n)]=(3m+n)(3n-m)=3n²+5mn-3m²