已知:x-y=10,y-z=15,x+z=20,求x²-z²的值
来源:学生作业帮助网 编辑:作业帮 时间:2024/06/11 20:37:20
已知:x-y=10,y-z=15,x+z=20,求x²-z²的值
分别把这三个式子编号①②③,那么②+③可得:
x+y=35
而x2-y2=(x+y)(x-y)=10*35=350
x²-z²
=(x+z)(x-z)
=(x+z)(x-y+y-z)
=20*25
=500.
x-y=10,y-z=15两式相加得x-z=25
x-z=25,x+z=20两式相加得x=22.5,则z=-2.5
x²-z²=22.5²-(-2.5)²=500
x-y = 10 ;①
y-z = 15 ;②
x+z= 20 ;③
①+②得:
x-z= 25 ;④
③+④得:
x=22.5
④-③得:
z= -2.5
x²-z² = 500
x-y=10------------(1)
y-z=15------------(2)
x+z=20------------(3)
(2)+(3)得
x+y=35-------------(4)
(4)+(1)得
2x=45
x=45/2
代入(3)得
z=20-x=20-45/2
=-5/2
x²-z²=(45/2)^2 -(5/2)^2
=500
:x-y=10为式子(1)
y-z=15 (2)
x+z=20 (3)
(1)+(2)=X-Z=25
x²-z²=(x+z)(X-Z)=20x25=500
x-y=10,y-z=15,x+z=20
x=45/2 y=25/2 z=-5/2
x²-z²=(45/2 )^2-(-5/2)^2=2000/4=500
最安全的方法是解出现xz带入,但是可能不是最快
已知 x/(y+z)+y/(z+x)+z/(x+y)=1求 (x*x)/(y+z)+(y*y)/(x+z)+(z*z)/(x+y)=?
x+y+z=15 x+5y+10z=70 x,y,z,各是几?
x+y+z=15 x+5y+10z=70 x,y,z,各是几?
X+Y-Z=15 X+5Y+10Z=70 求:X、Y、Z
已知(x+y)(x+z)=x,(y+z)(y+x)=2y,(z+x)(z+y)=3z,求x,y,z
已知 (x+y-z)/z=(x-y+z)/y=(y+z-x)/x,且xyz≠0,求代数式 ((x+y)(y+z)(x+z))/xyz
分式加减法:已知x+y/z=x+z/y=y+z/x(x+y+z≠0),求x+y-z/x+y+z
已知x+y/z=x+z/y=y+z/x(x+y+z≠0),求x+y-z/x+y+z的步骤
已知x+y/z=x+z/y=y+z/x(x+y+z≠0),求x+y-z/x+y+z的步骤
已知:x^2/(z+y)+y^2/(x+z)+z^2/(x+y)=0,求x/(z+y)+y/(x+z)+z/(x+y)的值.
已知:x-y=10,y-z=15,x+z=20,求x²-z²的值
(x+y-z)(x-y+z)=
X+Y+Z=15 X+5Y+10Z=70,Y.Z的值
已知x+y+z=0求证x*x*x+y*y*y+z*z*z=3xyz
已知(y+z)/x=(z+x)/y=(x+y)/z,则(y+z)/x的值是多少
已知X+Y+Z=0,求(X+Y)(Y+Z)(X+Z)+XYZ的值.
已知x+y+z=0,求(x+y)(y+z)(z+x)+xyz的值
已知x+y+z=0,求(x+y)(y+z)(x+z)+xyz的值