
八年级数学答案 CBCDB ABBDC DA 二、13. 6a2b2 14.(答案不唯一) 15. BC=BE(答案不唯一) 16. x=﹣3. 三、17.解:方程两边都乘以(x﹣2)得 5x=x﹣2+6...........................................................................................3分 5x﹣x=﹣2+6.......................................................................................4分 4x=4..................................................................................................5分 x=1.................................................................................................6分 检验:当x=1时,x﹣2≠0 ∴原分式方程的解为x=1.....................................................................7分 18.(1) d = 3,c = 2.........................................................................4分 (2)把 c = 2,d = 3 代入得 ....................................................................................6分 因为分式的值为正整数,所以 x+2 是 9 的正因数,9 的正因数有 1、3、9.当x+2 = 1 时,x =﹣1;当 x+2 = 3 时,x = 1;当 x+2 = 9 时,x = 7. ∴整数x的值可能为﹣1,1,7.....................................................9分(写对一个得1分) 19.解:(1)......................................................................................2分 .........................................................................3分 .............................................................................4分 =1..........................................................................................................5分 (2)∵|2c+4|与互为相反数, ∴ ∴2c+4=0,d﹣4=0 ∴c=-2,d=4....................................................................................7分 ∴2c+3d=2×(-2)+3×4=8, 则2c+3d的立方根为....................................................................8分 20.证明:∵AE∥DF ∴∠A=∠D...........................................................................2分 ∵BF∥CE ∴∠ACE=∠DBF.................................................................4分 又∵AB=CD, ∴AB+BC=CD+BC即AC=DB..............................................5分 在△ACE和△DBF中, , ∴△ACE≌△DBF(ASA)....................................................8分 21.解:(1)乙、丁.............................................................................2分 (2)原式.................3分 ...............................4分 ..............................................5分 ............................................................6分 (3)由于a+1≠0,a≠0,所以a≠﹣1,a≠0, 所以a=1.............................................................7分 当a=1时,原式..................9分(直接写a=1不扣分) 22.解:(1)(答案不唯一)....................3分 (2)a+b=0......................................................................6分 (3)∵与的值互为相反数, ∴2x﹣5+1﹣x=0, 解得x=4.........................................................................8分 ∴2x+1=9, ∴..........................................................9分 (1)证明:∵AD⊥BC于点D, ∴∠ADC=∠BDF=90°... ... ...
~~ 您好,已阅读到文档的结尾了 ~~