初二代数
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解决时间 2021-10-03 16:25
- 提问者网友：留有余香
- 2021-10-03 12:23
初二代数
最佳答案
- 五星知识达人网友：拾荒鲤
- 2021-10-03 12:37
(1): x^2-xy+xz-yz=x(x-y)+z(x-y)=(x-y)(x+z)x^2+xy+xz+yz=x(x+y)+z(x+y)=(x+y)(x+z) [(2x+z-y)/ (x^2-xy+xz-yz)]-[(2x+y+z)/(x^2+xy+xz+yz)] =[(2x+z-y)/ (x-y)(x+z)]-[(2x+y+z)/(x+y)(x+z)]=[1/(x+z)]×{[(2x+z-y)/ (x-y)]-[(2x+y+z)/(x+y)]}=[1/(x+z)]×[(x(2x+z)-xy+y(2x+z)-y＾-x(2x+z)-xy+y()2x+z++y＾)/(x＾-y＾)]=[1/(x+z)]×[(2y(2x+z)-2xy)/(x＾-y＾)]=[1/(x+z)]×[2y(2x+z-x))/(x＾-y＾)]=2y/(x＾-y＾) 1 1 1 (2) (a+ --- + 1 )(a+ --- - 1)(a - --- ) a a a [a+(1/a)+1][(1+1/a)-1]×[(a-(1/a)]={[a+(1/a)]＾-1}×[(a-(1/a)]=[a＾+(1/a)＾+1] ×[(a-(1/a)]= a＾3-a+(1/a)-(1/a)＾3+a-(1/a)=a＾3-(1/a)＾3(3)已知：x满足x^2-7x-1=0,则x^4+ (1/x^4 )---- 的值是? 解: x^2-7x-1=0 x-(1/x)=7 x^-2+(1/x)^=49 x^+(1/x)^=51 x^4+ (1/x^4 )=51×51-2=2599
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