a/(x+2)+b/(x-2)=(ax-2a)/(x²-4)+(bx+2b)/(x²-4)=[(a+b)x+(2b-2a)]/(x²-4)因为a/(x+2)+b/(x-2)=4x/(x²-4)即[(a+b)x+(2b-2a)]/(x²-4)=4x/(x²-4)所以 a+b=4 2a-2b=0解得a=2 b=2
