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Numerical Ability
Quadratic Equations
If x + y + z = 0 then,
x^2 + y^2 + z^2/(x-y)^2 + (y-z)^2 + (z-x)^2 = ?
A.0
B.1
C.xyz
D.x+y+z
E.None
Read Solution (Total 8)
-
- Edited::
=>(x + y + z)² = x² + y² + z² + 2xy + 2xz + 2yz
=> x + y + z = 0 given
=>So, x² + y² + z² = - 2(xy + xz + yz) .....(1)
(x² + y² + z²)
------------------- = ?
(x-y)²+(y-z)²+(z-x)²
(x² + y² + z²)
------------------------------------
2(x² + y² + z²)- 2(xy + xz + yz)
(x² + y² + z²)
------------------------------- [:: from (1)]
2(x² + y² + z²) + x² + y² + z²
(x² + y² + z²)
------------------ .........[::if x,y,z != 0, excluding the trivial case]
3(x² + y² + z²)
=> ans 1/3 (d)None
- 10 years agoHelpfull: Yes(48) No(0)
- (E) substitute your own values satisfying x+y+z=0 , let x=0,y=1,z=-1 and solve you get 1/3, substitute any values by your choice you get the same ans . let x=1,y=1,z=-2 . and any other . so none is the answer
- 10 years agoHelpfull: Yes(14) No(0)
- =>(x + y + z)² = x² + y² + z² + 2xy + 2xz + 2yz
=> x² + y² + z² = - 2(xy + xz + yz) .....(1)
(x² + y² + z²)
=>Given, ------------------- = ?
(x-y)²+(y-z)²+(z-x)²
(x² + y² + z²)
=>So, ------------------------------------
2(x² + y² + z²)- 2(xy + xz + yz)
(x² + y² + z²)
=> ----------------------------------- [:: from (1)]
2(x² + y² + z²) + x² + y² + z²
(x² + y² + z²) 1
=> ------------------ = - [::if x,y,z != 0]
3(x² + y² + z²) 3
=> ans (d)None - 10 years agoHelpfull: Yes(2) No(2)
- e.none
(x+y+z)^2= - 10 years agoHelpfull: Yes(0) No(0)
- Option (E)
- 10 years agoHelpfull: Yes(0) No(0)
- option E(none)
- 10 years agoHelpfull: Yes(0) No(0)
- given
x+y+z=0
and we know that
(x+y+z)^2=X^2+y^2+z^2+2(xy+yz+zx)
and
from first eqation x+Y+z=0
so
x^2+y^2+z^2=-2(xy+yz+zx)
now to find the value of given eq.
(x-y)^2+(y-z)^2+(z-x)^2=2(x^2+y^2+z^2)-2(xy+yz+zx)
puting the value of eq 2 in above eq we get
2(-2(xy+yz+zx)-2(xy+yx+zx)=-8(xy+yx+zx)
so now putting this value in the que we get
-2(xy+yz+zx)/-8(xy+yz+zx)=1/4
so answer is none E. - 10 years agoHelpfull: Yes(0) No(3)
- ans is E .. use (a+b+c)^2 and (a-b)^2
- 10 years agoHelpfull: Yes(0) No(0)
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