2a分之1减去a-b分之1乘以（2a分之a-b减去a的平方加上b的平方）,其中a=3减去2根号2,b=3根号2减去3,救命

1/2a-1/(a-b)*[(a-b)/2a-a^2+b^2]
=1/2a-1/(a-b)*[(a-b)/2a-(a^2-b^2)]
=1/2a-1/(a-b)*(a-b)/2a+1/(a-b)*(a^2-b^2)
=1/2a-1/(a-b)*(a-b)/2a+1/(a-b)*(a-b)(a+b)
=1/2a-1/2a+(a+b)
=a+b
=3-2√2+3√2-3
=√2