=(6²-4²)/4
=(36-16)/4
=20/4
=5
=(6^2-4^2)/4
=(36-16)/4
=20/4
=5.
y=1
xy=5
若x+y=6,x-y=4,求xy的ŀ
xy=[(x+y)²-(x-y)²]\/4 =(6²-4²)\/4 =(36-16)\/4 =20\/4 =5
初二数学问题:已知x+y=6,xy=4 求(x-y)²
(x-y)^2=(x+y)^2-4xy=20
已知x+y=6,xy=4,则x²+y²=
解：x+y=6 xy=4 x^2+y^2 =(x+y)^2-2xy =x^2+y^2 =(x+y)^2-2xy =6^2-2*4 =36-8 =28
已知x+y=6,xy=4.(1)求x平方+y平方的值;(2)求(x-y)平方的值;(3)求x...
(1)x²+y²=(x+y)²-2xy=6²-2*4=28 (2)(x-y)²=x²+y²-2xy=28-2*4=20 (3)x⁴+y⁴=(x²+y²)²-2x²y²=28²-2*4²=752 ...
已知(x+y)=16,(x-y)=4,求xy的ŀ
(x+y)=16,(x-y)=4 两式相加得 2x=20 x=10 y=6 xy=60
xy=-4,x十y=6。x,y各是多少
解法一：由题意知x、y是方程z²-6z-4=0的两个根 z²-6z+3²=4+9 (z-3)²=13 z-3=±√13 z=3±√13 ∴x=3+√13、y=3-√13或x=3-√13、y=3+√13 解法二：∵xy=-4 ∴y=-4\/x x-4\/x=6 x²-6x-4=0 同上解得x=3±√13 y=3士√13...
初二数学题!求解。已知x+y=6,xy=4,x>y,则√x-√y\/√x+√y=?
(√x-√y)\/(√x+√y)=(√x-√y)²\/(x-y)=(x+y-2√xy)\/(x-y)√xy=2 x-y=√(x+y)²-4xy=√20=2√5 (√x-√y)\/(√x+√y)=2\/2√5 =√5\/5
已知x+y=6.xy=4.求下列格式的值。(1)x^2+y^2(2)(x-y)^2(3)x^4+y^4
。（1）x^2+y^2 =(x+y)²-2xy =36-2*4 =28;（2）（x-y）^2 =(x+y)²-4xy =36-4*4 =20;（3）x^4+y^4 =(x²+y²)²-2x²y²=28²-2*4*4 =784-32 =752
如果x+y=6,x-y=2 求(1)代数式xy的值。 (2)代数式x(3y-2x)+2y(x-
回答：由方程得 x=4 y=2 即 xy=8 x(3y-2x)+2y(x-y)=4*(6-8)+4(4-2)=-8+8=0
若x+y=6,xy=4,且x>y,则代数式根号x+根号y分之根号x-根号y的值为_百度...
∵x+y=6,xy=4 ∴(√x-√y)²=x+y-2√(xy)=6-2√4=2 ∵x>y ∴√x-√y>0 ∴√x-√y=√2 又(√x+√y)²=x+y+2√(xy)=6+2√4=10 ∴√x+√y=√10 ∴（√x-√y)\/(√x+√y)=√2\/√10 =1\/√5 =√5\/5 ...
