電子課本網(wǎng) › 第83頁(yè)

第83頁(yè)

信息發(fā)布者：

$解：原式?=\frac {(x-y)2+4xy}{x-y}×\frac {(x+y)2-4xy}{x+y}?$

$?=\frac {x2-2xy+y2+4xy}{x-y}×\frac {x2+2xy+y2-4xy}{x+y}?$

$?=\frac {(x+y)2}{x-y}×\frac {(x-y)2}{x+y}?$

$?$=x2-y2$?$

$解：原式?=1-\frac {a-1}{a}÷\frac {a2-1}{a(a+2)}?$

$? =1-\frac {a-1}{a}×\frac {a(a+2)}{(a-1)(a+1)}?$

$? =1-\frac {a+2}{a+1}?$

$ =-\frac {1}{a+1}?$

$解：? 2x=3(x- 1)??\ $

$x=3?$

$檢驗(yàn)：當(dāng)?x= 3?時(shí)，?x(x- 1)≠0?$

$∴?x=3?是方程的解$

$解：?5(y2-y)=y2+y??\ $

$4y2=6y?$

$解得?y=0?或?y=\frac {3}{2}?$

$檢驗(yàn)：當(dāng)?y=0，??y2+y=0，?$

$∴舍去當(dāng)?y=\frac {3}{2}?時(shí)，?y(y+1)(y-1)≠0?$

$∴?y=\frac {3}{2}?是方程的解$

$解：?3(5x-4)=2(2x+5)-3(x-2)??\ $

$x=2$

$?檢驗(yàn)：當(dāng)?x=2?時(shí)，?6(x-2)=0$

$??x= 2?是增根，原方程無(wú)解$

$解：? (x-2)2+4=x2-4??\ $

$x=3?$

$檢驗(yàn)：當(dāng)?x= 3?時(shí)，?(x+ 2)(x-2)≠0?$

$∴?x=3?是方程的解$

$解：設(shè)乙隊(duì)全部完成此項(xiàng)工程需要?x?個(gè)月$

$?\frac {1}{2}(\frac {1}{x}+\frac {1}{3})+\frac {1}{3}=1?$

$? x= 1?$

$?\frac {1}{x}＞\frac {1}{3}?$

答：乙隊(duì)的施工速度快。

$解：?\frac {a}{a+1}-\frac {a+1}{a+2}=\frac {a(a+2)-(a+1)2}{(a+1)(a+2)}=\frac {a2+2a-a2-2a-1}{(a+1)(a+2)}=-\frac {1}{(a+1)(a+2)}?$

$∵?a＞-1?$

$∴?a+1＞0，??a+2＞0?$

$∴?-\frac {1}{(a+1)(a+2)}＜0?$

$∴?\frac {a}{a+1}＜\frac {a+1}{a+2}?$

亚洲激情+欧美激情,无码任你躁久久久久久,我的极品美女老婆,性欧美牲交在线视频,亚洲av高清在线一区二区三区