已知x方减x加1分之x=7,则 的值为

设x+1/x=t,平方得:x^2+1/x^2+2=t^2x^2+1/x^2=t^2-2原方程变为:(t^2-2)-3t-8=0t^2-3t-10=0(t-5)(t+2)=0t=5或t=-2.即x+1/

x的4次方减7x的平方加1等于0x^4-7x^2+1=0x^2-7+1/x^2=0x^2+1/x^2=7x^2-1+1/x^2=6x^2+2+1/x^2=9(x+1/x)^2=9x+1/x=±3x的三

由题意可得：x+1/x-1=7(x+1/x)^2=64所以x^2+1/x^2=62所以(x^4+x^2+1)/x^2=x^2+1+1/x^2=63再问：我看不懂，您能解释详细点吗？谢谢了再答：（x^2

1.y'=sinx+xcosx2.

x/(x^2-x+1)=71/(x-1+1/x)=7x-1+1/x=1/7x+1/x=8/7x^2/(x^4+x^2+1)=1/(x^2+1+1/x^2)=1/[(x+1/x)^2-1]=1/[(8/

X方-X+1分之X=7(x²-x+1)/x=1/7x-1+1/x=1/7x+1/x=8/7X四次方+X二次方+1分之X二次方分子分母同时除以x²=1/(x²+1+1/x&

由于1/(x^2-x+1)=1/6则x^2-x+1=6再由求根公式求出x,代入后面式子计算

x=1/(2+√3)xy=1y=(2+√3)x=1/(2+√3)x=(2-√3)/(2+√3)(2-√3)x=2-√3(x^2y-xy^2)/(x^2-y^2)=xy(x-y)/(x+y)(x-y)=

x的平方分之x的四次方加1=（x*x*x*x+1）/（x*x)=x*x+1/（x*x)由于x+1/x=a,所以（x+1/x）*（x+1/x)=x*x+2+1/（x*x)=a*a则有x*x+1/（x*x

x²+2xy+4y²+x²y²+1=8xy(x²-4xy+4y²)+(x²y²-2xy+1)=0(x-2y)²

正负根号5

∵x平方加4x=1;(x+2)^2=5∴x=±√5-2∴x五次方+6x四次方+7x三次方-8x+1=x^5+4x^4+2x^4+8x^3-x^3-8x+1=x^3(x^2+4x)+2x^2(x^2+4

已知:(x-1)(y-2)-x(y-3)=8,那么：xy-2x-y+2-xy+3x=8化简得：x-y=6所以：2分之(x²+y²）-xy=2分之(x²+y²-2

x^2+x=1x^3+x^2=x(x^2+x)=x原式x^2+1/x=1/x(x^3+1)=1/x(x^3+x^2+x)=1/x*2x=2

x的平方分之x的四次方加1=x²+x²分之1=x²+2+x²分之1-2=(x+x分之1)²-2=3²-2=9-2=7

x²-x-1=0x²=x+1x^4=(x+1)²=x²+2x+1=(x+1)+2x+1=3x+2x^5=x^4*x=(3x+2)*x=3x²+2x=3

(x＋y)/(x)=31＋(y/x)=3得：y/x=2则：(x²＋y²)/(x²－xy＋y²)【分子分母同除以x²】=[1＋(y/x)²]/

由x³+x²+x+1=0,可得x=0所以1+x+x²+x³+x^4=1+0=1或者变形：1+x+x²+x³+x^4=1+（1+x+x

x/(x^2-x+1)=7,(x^2-x+1)/x=1/7x+(1/x)-1=1/7x+(1/x)=8/7x^2/(x^4+x^2+1)=1/[(x^4+x^2+1)/x^2]=1/[x^2+(1/x

椭圆半焦距：2a^2-2b^2双曲线半焦距：a^2+b^2有相同焦点,2a^2-2b^2=a^2+b^2a^2=3b^2椭圆半焦距：c^2=2a^2-2b^2=4b^2椭圆半焦距c=2b椭圆半长轴=根