2x-y 3z=1 2x 2z=6 4x 2y 5z=4

1.3y²zdy+y³dz=cosxdx-e^xdz整理:(y³+e^z)dz=cosxdx-3y²zdydz=[cosx／(y³+e^z)]dx-[

(6x+12)/(x²+4x+4)+(x²-4x+4)/(x²-4)=(x²-4)/(x²-4x+4)6(x+2)/(x+2)²+(x-2)

1x+2x+3x+4x+5x+6x+7x+8x+9x+10x+11x+12x+13x+14x+15x=550120x=550x=55/12=4.583

5X-4Y+4Z=13①2X+7Y-3Z=19②3X+2Y-Z=18③将③*4+①得17X+4Y=85④将③*3-②得7X-Y=35⑤将⑤*4+④得X=5将X=5代入①得Y=0将X=5,Y=0代入③得

x+9x=6x*2+1212x-x-9x=-122x=-12x=-12÷2x=-6x+9-x/3=4两边乘33x+9-x=123x-x=12-92x=3x=3÷2x=3/2

2x(x-1)-x(3x+2)=-x(x+2)-122x^2-2x-3x^2-2x=-x^2-2x-122x^2-3x^2+x^2-2x-2x+2x=-12-2x+12=0-2(x-6)=0x-6=0

(x+2-12/x-2)/(4-x)/(x-2),其中x=-1/2=(x²-4-12)(x-2)÷(4-x)/(x-2)=(x²-16)/(4-x)=-(4-x)(4+x)/(4-

提出x得到：x*(1-1/2+1/2-1/3+1/3-1/4……+1/2008-1/2009)=2008接着：x*(1-1/2009)=2008最后：x=2009

解方程x=25x/28+9,得3x/28=9,得x=84

每个绝对值里都是正数所以原式=x+1+x+3+x+5+……+x+13-x-2-x-4-x-6-……-x-12=x-1*6+13=x+7=π/2+7

从上面两个方程,解出来X与Y,用Z来代替,然后代入最后的代数式,OK!再问：具体步骤。。。。。。。。再答：就象解方程一样啊，只是把Z看成常数再问：还是不懂你说的啥子意思。。再答：根据题意：4x-3y=

只要答案吗.看见ZY2,ZY3就想多化合价元素.比如S.先推ZY2,ZY3分别为SO2,SO3.X2Z为X2S,也就是说.X是1A族的元素.又在第三周期,为Na.Na2S+H2SO4===>可以发生归

x-o.8x=6X=3012x-8x=4.8X=1.23x-8=16X=8x-0.7x=3.6X=127.5x-2x这题没有=

60X+15X+10X+6X=12091X=120X=120/91

x/2+x/6+x/12+x/20+x/30+x/42=136x/42=1x=7/6

x=±1,y=±3,z=±2xyzz>y则0>x>z>yx=-1,y=-3,z=-2,x2y-[4x2y-(xyz-x2z)-3x2z]-2xyx=x2y-4x2y+xyz-x2z+3x2z-2xyx

/>X  /-2/=2    y不用变  Z=0解原式是x2-[4xy2-(xyz-x2z0-3x2z]-2xyz=4-

=x^2+10x-24+x^2+15x+56-x^2+5x+50=x^2+30x+82=4+60+82=146其实,不化简,直接代入=14*0+9*10+7*8=0+90+56=146也很简单

原方程化为：（1/2+1/6+1/12+1/20+1/30+1/42)x=6【(1-1/2)+(1/2-1/3)+(1/3-1/4)+(1/4-1/5)+(1/5-1/6)+(1/6-1/7)】x=6

1,应该是x是几次幂就有几个根吧,所以应该是7+2=9个2.-7.036622145,-6.489288572,-6.200988153,-4.734373320,-4.289168546,-2.77