5.4分式的加减(一)———同分母分式加减比一比•同分母分数的加减•同分母分式的加减9491949595941919451411xxaaa3315x133aaaa同分母分式的加减法法则:•同分母分式相加减,分母不变,把分子相加减acbacabxx32xyx32abxabx3131abxabx3131x1xy32030ababxx311abxx311abx322小结:如果分子是多项式,在进行减法时要先把分子用括号括起来。算一算xx2321xyx322232xyx3332xyxx22xyx32232xy3332xyxx1xy323332xyx332xy2232xyx典型例题3(1)abababab22222112(2)()()xyxyxyyx练一练31215(1)aaa13(2)mm(3)yxxyxy22(5)ababab2222(6)acbcabab22(4)()()ababba先化简,再求值22211,3.22xxxxxxx其中典型例题2(2)22ababba42(3)22xxx(1)aaxyyx练一练