数学分式整式题1.a+1/a=10,求(a-1/2)的平方2.a^m=3 a^n=2,求a^2m-n3.已知1/a-1/

数学分式整式题
1.a+1/a=10,求(a-1/2)的平方
2.a^m=3 a^n=2,求a^2m-n
3.已知1/a-1/b=4,求a-2ab-b/2a-2b+7ab
没抄错就是(a-1/2)的平方

1.(a-1/a)^2
=a^2-2*a*(1/a)+(1/a^2)
=a^2+(1/a)^2-2
=[a+(1/a)]^2-2*a*(1/a)-2
=10^2-4
=96;
2.a^(2m-n)
=a^(2m)/(a^n)
=(a^m)^2/(a^n)
=3^2/2
=9/2;
3.因为1/a-1/b=4,
所以(b-a)/(ab)=4,
所以b-a=4ab,
所以a-b=-4ab,
所以(a-2ab-b)/(2a-2b+7ab)
=[(a-b)-2ab]/[2(a-b)+7ab]
=(-4ab-2ab)/(-8ab+7ab)
=-6ab/(-ab)
=6.