____
对下面句中划线词的释义全部正确的一项是( )
已知:2+ 23 =22× 23 ,3+ 38 =32× 38 ,4+ 415 =42× 415 ,5+ 524 =52× 524 …,若6+ ba =62× ba 符合前面式子的规律,
则a+b=____.