15.下列运算正确的是( )
0 283489 283497 283503 283507 283513 283515 283519 283525 283527 283533 283539 283543 283545 283549 283555 283557 283563 283567 283569 283573 283575 283579 283581 283583 283584 283585 283587 283588 283589 283591 283593 283597 283599 283603 283605 283609 283615 283617 283623 283627 283629 283633 283639 283645 283647 283653 283657 283659 283665 283669 283675 283683 366461
| A. | (ab)3=a3b | B. | $\frac{-a-b}{a+b}$=-1 | C. | a6÷a2=a3 | D. | (a+b)2=a2+b2 |