∴原式=(X+Y)²-5XY
=(2√3)²-5×2
=12-10
=2。
已知x=根号3+1,y=根号3-1,求代数式x^2-3xy+y^2的值
xy=（√3+1）（√3-1）=3-1=2 ∴x^2-3xy+y^2 =(x-y)^2-xy =2^2-2 =4-2 =2
已知x=根号3+1,y=根号3-1,求代数式x^2-3xy+y^2的值
X+Y=2√3，XY=(√3+1)(√3-1)=3-1=2，∴原式=(X+Y)²-5XY =(2√3)²-5×2 =12-10 =2。
已知x=√3+1,y=√3-1,求代数式x⊃2;-y⊃2;\/x⊃2;y+xy⊃2;的...
解；原式=x²-y²\/xy(x+y)=x²-y\/x(x+y)当x=√3+1,y=√3-1,时。原式=（√3+1)²-(√3-1,)\/(√3+1）2√3 =4+2√3-（4-2√3）\/4√3 =4+2√3-√3\/3+1\/2 =4.5+5√3\/3
2.已知:x=根号3+1,y=根号3-1,求下列各式的值: (1)x的平方-y的平方 (2...
x=√3+1 ,y=√3-1 x+y=2√3 x-y=2 xy=2 x^2-y^2=(x-y)(x+y)=2*2√3=4√3 x^2+xy+y^2=(x+y)^2-xy=(2√3)^2-2=10
已知X=根号3+1,Y=根号3-1,求下列各式的值:
已知X=根号3+1，Y=根号3-1，求下列各式的值：x+y=根号3＋1＋根号3-1=2根号3 xy=(根号3)²-1²=3-1=2 x-y=2 所以 (1)X的平方+2XY+Y的平方 =(x+y)²=(2根号3)²=12 （2）X的平方-Y的平方 =(x+y)(x-y)=2根号3 ×2 =4根号3 ...
已知x=根号3+1,y=根号3-1,求x方-y方\/x方y+xy方的值。
x方-y方\/x方y+xy方 =(x+y)(x-y)\/[xy(x+y)]=(x-y)\/xy =[(√3+1)-(√3-1)]\/[(√3+1)(√3-1)]=2\/2=1
已知x=(根号3)+1,y=(根号3)-1,求代数式(x-y;\/x-y)-(3xy+3xy;\/x+2xy+...
（x-y;\/x-y）-（3xy+3xy;\/x+2xy+y） =(x+y)(x-y)\/(x-y)-3xy(x+y)\/(x+y)^2 =x+y-3xy\/(x+y) =2√3-3(3-1)\/2√3 =2√3-√3 =√3
1.已知y\/x=3,求x+y\/x-y 2.已知X=根号3+1,y=根号3-1,求XX-YY\/XXY+XYY
(x^2-y^2)\/(x^2y+xy^2)=(x+y)(x-y)\/[xy(x+y)]=(x-y)\/(xy)=(√3+1-√3+1)\/(√3+1)(√3-1)=2\/2 =1 Y为正数 y=x^2\/(2-3x)x^2\/(2-3x)>0 (2-3x)>0 x<2\/3 Y为负数 x^2\/(2-3x)<0 (2-3x)<0 x>2\/3 Y=0 x^2=0 x=0 分式无意义 2-3x=0...
若x=(根号3)+1,y=(根号3)-1,求x+(根号xy)\/[(根号xy)+y]+(根号xy)-y\/...
x+(根号xy)\/[（根号xy)+y]+(根号xy)-y\/x-(根号xy)=(√3+√2+1)\/(√3+√2-1)+(1+√2-√3)\/(√3-√2+1)=[(√3+√2+1)(√3-√2+1)]\/[(√3+(√2-1))(√3-(√2-1))]+[(1+√2-√3)(1-√2+√3)]\/[(√3+(√2-1))(√3-(√2-1))]=[(√3+1)...
已知x等于2倍跟号3加1,y等于2倍跟号3减1,求x的平方减4xy加的y平方?
x=2根号3+1 y=2根号3-1 x²-4xy+y²=x²-2xy+y²-2xy=(x-y)²-2xy =[（2根号3+1-（2根号3-1）]²-2*(2根号3+1)*(2根号3-1)=2²-2*[(2根号3）²-1]=4-2*(12-1)=-18 ...
