第3个回答 2015-06-21
13; 原式=2x/(x+1)-2(x+3)/(x+1)(x-1) X(x-1)^2/(x+3)
=2x/(x+1)-2/(x+1) X (x-1)
=2/(x+1),
14; 原式=(x-2)^2/2x X x/(x-2) +1=(x-2)/2+1=x,, 原式=-2,-1,0,1,2
15; 原式=2a/(a^2-4) X (a-2)/2a=1/(a-2), a=2-√2 ,原式=-√2/2
16; 原式=(x+2)(x-2)/(x+3)(x-3) X (x-3)/(x-2)=(x+2)/(x+3)
2x-3<7, x<5 , x=1,2,3,4 , 原式=3/4, 4/5,5/6, 6/7