13.下列等式一定成立的是( )
0 283491 283499 283505 283509 283515 283517 283521 283527 283529 283535 283541 283545 283547 283551 283557 283559 283565 283569 283571 283575 283577 283581 283583 283585 283586 283587 283589 283590 283591 283593 283595 283599 283601 283605 283607 283611 283617 283619 283625 283629 283631 283635 283641 283647 283649 283655 283659 283661 283667 283671 283677 283685 366461
| A. | a2+a3=a5 | B. | (a+b)2=a2+b2 | C. | (2a2b3)2=6a3b6 | D. | (a+1)(a-1)=a2-1 |