4z平方-(x y)平方
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2x²+2xy+y²-4x+z-2倍根号z-3+2=0可化为x²+2xy+y²+x²-4x+4+(z-3)-2倍根号(z-3)+1=0即(x+y)
3x的平方乘y-[2x的平方乘y-(2xy的平方-x的平方乘z)-4x的平方乘z]-xyz,当x=2,y=3,z=1时,求值=3x²y-2x²y+2xy²-x²
答:x的平方+y的平方+z的平方=xy+yz+xzx²+y²+z²=xy+yz+xz两边同乘以2:2x²+2y²+2z²=2xy+2yz+2
设x/2=y/3=z/4=a则:x=2a;y=3a;z=4a代入得:(xy+yz+zx)/(x^2+y^2+z^2)=(6a^2+12a^2+8a^2)/(4a^2+9a^2+16a^2)=26a^2
x²+y²+z²-xy-yz-xz=(1/2)(2x²+2y²+2z²-2xy-2yz-2zx)=(1/2)(x²-2xy+y
令a=x/3=y/4=z/6x=3ay=4az=6a所以原式=(12a²+24a²+18a²)/(9a²+16a²+36a²)=54a&su
应该是2x+5y-4=02x+5y=4原式=2^2x×2^56=2^(2x+5y)=2^4=16假设锐角是A和B则有sin²A+sin²B=1所以就是x1²+x2&sup
设x/2=y/3=z/4=a,则x=2a,y=3a,z=4axy+yz+xz=2a*3a+3a*4a+4a*2a=26a*axx+yy+zz=2a*2a+3a*3a+4a*4a=29a*a则结果为26
处理这类比例问题,有一个通用方法如果:x:y:z=a:b:c可以设x=aky=bkz=ck带入计算,就行了自己来试试吧~
设x/2=y/3=z/4=k∴x=2k,y=3k,z=4k∴(xy+yz+zx)/(x²+y²+z²)=(6k²+12k²+8k²)/(4k
令3分之x=4分之y=6分之z=kx=3k,y=4kz=6k(xy+yz+xz)/(x^2+y^2+z^2)=k^2(12+18+24)/k^2(36+16+9)=54/61
能拍下来吗?再问:额再问:不清再答:是再问:速度啊大神再问:说啊再答:稍等再问:哦哦再答:再答:
设k=x/2=y/3=z/4所以x=2ky=3kz=4k原式=6k*+12k*+8k*/4k*+9k*+16k*=26/29
直接作差,然后配方5x^2+y^2+z^2-2xy-4x-2z+2=(4x^2-4x+1)+(x^2-2xy+y^2)+(z^2-2z+1)=(2x-1)^2+(x-y)^2+(z-1)^2结果是三个
设x/3=y/4=z/5=t则x=3t,y=4t,z=5t∴(xy+yz+zx)/(x²+y²+z²)=(12t²+20t²+15t²)/(
x^3z-4x^2yz+4xy^2z=xz(x^2-4xy+4y^2)=xz(x-2y)^2(x+2)(x+3)+3x+1=x^2+3x+2x+6+3x+1=x^2+8x+7=(x+1)(x+7)x^
由题意得{x+y+z=02x-y-7z=0={x+z=-yβ2x-7z=ypβ+p得x=2z,把x=2z带入β=-3z当x=2z,β=-3z时原式=【3×2z×(-3z)-(4z)²】除以(
令3/x=4/y=6/z=1/k则x=3ky=4kz=6k(x²+y²+z²)/(xy+yz+xz)=(9k²+16k²+36k²)/(12
解方程组:{2x-3y-z=0.(1){x+3y-14z=0.(2)(1)+(2)得:3x-15z=0即:x=5z,代入(1)式得y=3z所以:(4x²-5xy+z²)/(xy+y